Optical tracking system for airborne objects

ABSTRACT

An airborne object positioning system including a radiation emitter, a radiation receiver and a signal processor. Then the radiation emitter is adapted to direct radiation to a positioning area a defined distance from the radiation emitter, the radiation carrying a modulated location signal containing information corresponding to positions within the positioning area. The radiation receiver is adapted to receive at least a portion of the emitted radiation carrying the modulated signal and output a signal to the signal processor indicative of the modulation of the location signal of the received radiation. And the signal processor is adapted to process the outputted signal and identify a position within the positioning area indicative of the location in the positioning area of the received radiation.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a Continuation In Part of U.S. patentapplication Ser. No. 11/249,262, entitled Optical Tracking System forRefueling, filed on Oct. 14, 2005, the contents of which areincorporated herein by reference in its entirety, which in turn claimspriority to U.S. Provisional Patent Application Ser. No. 60/656,084,entitled Optical Tracking System for Refueling, filed on Feb. 25, 2005,the contents of which are incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

Aerial refueling is known. In an exemplary refueling scenario, arefueling drogue connected to a refueling hose is unreeled from arefueling aircraft (e.g., tanker aircraft) towards a receiver aircraft(an aircraft to be refueled), such as a fighter plane, a helicopter,etc. The receiver aircraft has a refueling probe extending from theaircraft. The receiver aircraft maneuvers to the refueling drogue andinserts its refueling probe into the refueling drogue, at which pointthe refueling drogue “locks” onto the refueling probe, and a transfer offuel from the refueling aircraft to the receiver aircraft is conducted.In an alternative exemplary refueling scenario, a refueling boom isconnected to the refueling aircraft, and the receiver aircraft is fittedwith a refueling boom receptacle, and the receiver aircraft maneuvers tothe refueling boom and/or the refueling boom is maneuvered to thereceiver aircraft until the boom mates with the receptacle on thereceiver aircraft.

SUMMARY OF THE INVENTION

In an exemplary embodiment of the present invention, there is anairborne object tracking system comprising, a radiation emitter, aradiation receiver and a signal processor, wherein the radiation emitteris adapted to direct radiation to a positioning area a defined distancefrom the radiation emitter, the radiation carrying a modulated locationsignal containing information corresponding to positions within thepositioning area, wherein the radiation receiver is adapted to receiveat least a portion of the emitted radiation carrying the modulatedsignal and output a signal to the signal processor indicative of themodulation of the location signal of the received radiation, and whereinthe signal processor is adapted to process the outputted signal andidentify a position within the positioning area indicative of thelocation in the positioning area of the received radiation.

In another embodiment of the invention, the radiation emitter is adaptedto emit a focused optical beam and scan the focused optical beam overthe positioning area.

In yet another embodiment of the invention, the emitted radiation is afocused optical beam, wherein the modulated location signal includes aplurality of digital data blocks, the plurality of digital data blockscontaining information respectively corresponding to a plurality ofdiscrete positions within the positioning area that respectivelycorrespond to a current location of the focused beam within thepositioning area.

In another embodiment of the invention, the radiation emitter is adaptedto emit a focused optical beam and scan the focused optical beam overthe positioning area.

In another embodiment of the invention, there is an airborne objecttracking system comprising a radiation emitter, a radiation receiver,and a signal processor, wherein the radiation emitter is adapted todirect a beam of emitted radiation to an area away from the radiationemitter, the radiation including discernable properties that vary in acorresponding manner with varying orientation of the beam of radiationwith respect to the radiation emitter, wherein the radiation receiver isadapted to receive at least a portion of the emitted radiation andoutput a signal to the signal processor indicative of one or more of thediscernable properties of the received radiation; and wherein theprocessor is adapted to process the outputted signal and identify afirst virtual orientation indicative of an orientation of the receiverrelative to the radiation emitter when at least a portion of theradiation was received by the receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an aerial refueling operation according to thepresent invention.

FIG. 2 is a front view of an aerial refueling operation according to thepresent invention.

FIG. 3 is a side view of a drogue assembly according to the presentinvention.

FIG. 4 is a side view of a scanning operation according to the presentinvention.

FIG. 5 is a top view of a scanning operation according to the presentinvention.

FIG. 6 is a view of a focused optical elongated beam emitted by theradiation emitter.

FIG. 7 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface.

FIG. 8 is a view of a focused optical elongated beam emitted by theradiation emitter over an elapsed time.

FIG. 9 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface over an elapsed time.

FIG. 10 is a view of a focused optical elongated beam emitted by theradiation emitter.

FIG. 11 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface.

FIG. 12 is a view of a focused optical elongated beam emitted by theradiation emitter over an elapsed time.

FIG. 13 is a view of a focused optical elongated beam emitted by theradiation emitter impinging on a flat surface over an elapsed time.

FIG. 14 is a view of a virtual grid.

FIG. 15 is a view of a virtual grid superimposed over a scanning area.

FIGS. 16-17 present a schematic representing a two-pass scan over thevirtual grid.

FIG. 18 depicts a location of the virtual grid with respect to theradiation emitter.

FIGS. 19-20 present a schematic representing a two-pass scan over thevirtual grid, with the receiver positioned within the grid.

FIG. 21 presents a schematic of another type of scan utilized in thepresent invention.

FIG. 22 presents a symbolic representation of a digital data setutilized in an embodiment of the present invention.

FIG. 23 presents a schematic representing row orientation with respectto receiver aperture for a small beam/large aperture configuration.

FIGS. 24 and 25 schematically represent drogue positioning without theuse of a virtual grid.

FIGS. 26 to 31 schematically represent various galvo designs.

FIGS. 32 to 33 b schematically represent beam emission in elapsed time.

FIGS. 34-40 schematically represent an emitter according to anembodiment of the present invention.

FIG. 41 is a side view of another aerial refueling operation accordingto the present invention.

FIG. 42 is a front view of the aerial refueling operation of FIG. 41.

FIG. 43 is a side view of receiver aircraft according to the presentinvention.

FIGS. 44-46 present an exemplary embodiment of an emitter in operationaccording to an embodiment of the present invention.

FIG. 47 presents an exemplary graph presenting sweep times (scan times)of a horizontal and vertical scan according to the present invention.

FIG. 48 presents an exemplary embodiment of a radiation receiveraccording to an embodiment of the present invention.

FIG. 49 presents an exemplary scenario where the number of scan linesreceived by the radiation receiver is utilized to determine slantdistance from the radiation emitter to the radiation receiver.

FIG. 50 presents exemplary fields of view of a radiation emitteraccording to an embodiment of the present invention.

FIGS. 51-54 present exemplary performance characteristics of anexemplary tracking system according to an embodiment of the presentinvention.

FIG. 55 presents an exemplary scan grid that may be obtained utilizingan embodiment of the present invention.

FIG. 56 present exemplary performance characteristics of an exemplarytracking system according to an embodiment of the present invention.

FIG. 57 presents an high-level exemplary conceptual diagram of a systemconfigured to address turbulence that may be used in the presentinvention.

FIG. 58 presents a schematic detailing overlapping fields of view of theradiation emitter.

FIG. 59 presents a schematic detailing an exemplary clock cycle of aradiation emitter according to an embodiment of the present inventionand how those exemplary clock cycles may be used to determine whetherthe system is in calibration.

FIG. 60 presents a high-level exemplary conceptual diagram of a systemconfigured for use with drogue tracking according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present inventors have determined that it is desirable that thelocation of an airborne object (e.g., a refueling drogue, a receiveraircraft in general, and a particular location on the receiver aircraft(e.g., the portion of the refueling probe that will interface with therefueling drogue/the receptacle in the receiver aircraft), etc.,) beidentified relative to a refueling aircraft during aerial refuelingoperations. The present inventors have further determined that it isdesirable that a system substantially maintain/adjust the position of areceiver aircraft, drogue, and/or refueling boom, or other airborneobject (or plurality of airborne objects), relative to a refuelingaircraft and receiver aircraft (or pertinent location thereon),respectively, so that mating of the receiver aircraft or other airborneobject with the refueling aircraft can be better executed. Accordingly,an embodiment of the present invention is directed towards systems,methods and apparatuses for enabling determination of the position,relative to a fixed reference point on the refueling aircraft, of anairborne refueling device attached to the refueling aircraft, and/ordetermination of the position, relative to a fixed reference point onthe refueling aircraft, of a receiver aircraft in general (or multiplereceiver aircraft in general), and, in particular, of a certain location(or plurality of locations) on the receiver aircraft.

Moreover, some embodiments of the present invention are directed towardssystems, methods and apparatuses for enabling a receiver aircraft ingeneral and a boom/receptacle of a receiver aircraft in particular, tosubstantially maintain a position relative to the fixed reference point(also known as station keeping) based on this determined position. In anexemplary embodiment, this fixed reference point is a radiation emitteron the wing of the refueling aircraft, as will be discussed below.Further embodiments of the present invention are directed towardssystems, methods and apparatuses for enabling a location of a refuelingdevice (drogue, boom, etc.), relative to a receiver aircraft, to bedetermined. Some exemplary embodiments of the present invention, coupledwith exemplary scenarios utilizing the present invention, will now bedescribed followed by detailed discussions of particular embodiments ofthe present invention.

In a first embodiment of the present invention, as may be seen in FIGS.1-3, there is a refueling drogue assembly 100 comprising a refuelingdrogue 105 connected to a distal portion of a refueling hose 110 (withrespect to the attachment of the hose 110 to the aircraft 1000) that isin turn connected to an aircraft 1000. The aircraft 1000 includes aradiation emitter 200 that emits an optical beam in the generaldirection of the drogue assembly 105 (in particular, towards thereceiver 300 on the drogue assembly 105, as will be discussed below).The beam is emitted in a scanning fashion such that the beam scans anarea in relation to the radiation emitter in which the drogue 105(receiver 300) is likely located, based on, for example, empiricaldata/analytical data for a given air speed, altitude, etc. This area isindicated by reference number 400 in FIGS. 1-3. The optical bean emittedby the radiation emitter 200 scans this area in a manner such that adiscernable property of the optical beam changes as the orientation ofthe beam, with respect to the radiation emitter 200, changes. Thediscernable property of the optical beam that varies, in a controlledmanner, with changing orientation of the beam with respect to theradiation emitter may be, for example, different discrete digital datablocks carried on the beam by way of beam modulation.

Accordingly, in an exemplary scenario utilizing the present invention,the optical beam scans over the scanning area 400 in a manner such thata discernable property of the optical beam changes as the beam isscanning over the scanning area. That is, the discernable property isdifferent when the beam is located at one portion of the scanning area,as opposed to another portion of the scanning area, owing to the changein orientation of the beam with respect to the radiation emitter and thescanning area. This discernable property is carried on the optical beamand changes in a predetermined manner such that an analysis of thisdiscernable property will enable the location of the beam, relative tothe scanning area, to be determined. In this scenario, the radiationreceiver 300 on the drogue assembly 100 is configured to output a signalto a signal processor 500 (after receiving/sensing the optical beam asit passes over the receiver) onboard the drogue assembly 100. Thisoutputted signal from the receiver 300 is indicative of the discernableproperty carried on the optical beam that is received by the receiver.The signal processor 500 contains software and/or sufficient look uptables stored in a memory such that the signal processor 500, once itreceives the signal from the receiver 300, may analyze the receivedsignal and determine that the discernable property is indicative of aspecific beam orientation with respect to the radiation emitter 200 andthe scanning area 400. Because the geometry of the scanning area 400relative to the radiation emitter is known, the location of the receiver300 within the scanning area 400 may thus be determined by comparing thediscernable property of the received radiation to information stored ina look-up table. Because the geometry of the refueling drogue assembly100 relative to the receiver 300 is known, the position of the drogueassembly 100 relative to the radiation emitter may be determined.

As may be seen from FIGS. 1-3, the scanning area 400 is a square area inspace that passes through the receiver 300 on the refueling drogueassembly 100. This area 400 is approximately normal to the direction oftravel of the focused beam away from the radiation emitter (this isdiscussed in greater detail below).

In another embodiment of the present invention, as may be seen in FIGS.41-43, there is a receiver aircraft 1105 including a receiver 300trailing refueling aircraft (e.g., tanker) 1000. The refueling aircraft1000 includes the radiation emitter 200 that emits an optical beam inthe general direction of the receiver aircraft 1105 (in particular,towards the receiver 300 on the receiver aircraft 1105, as will bediscussed below). As with the beam emission for the refueling drogueassembly application detailed above, a beam is emitted in a scanningfashion such that the beam scans an area in relation to the radiationemitter in which the receiver aircraft 1105 (receiver 300) is likelylocated, based on, for example, a given mission profile, real-timelocational data, etc. This area is indicated by reference number 400 inFIGS. 1-3. As in the refueling drogue assembly scenario detailed above,the optical bean emitted by the radiation emitter 200 scans this area ina manner such that a discernable property of the optical beam changes asthe orientation of the beam, with respect to the radiation emitter 200,changes.

An exemplary scenario utilizing the present invention parallels thatdetailed above with respect to the refueling drogue assembly, exceptthat in this scenario, the radiation receiver 300 is located on thereceiver aircraft 1105, which outputs a signal to a signal processor 500(after receiving/sensing the optical beam as it passes over thereceiver) onboard the receiver aircraft 1105 and/or onboard therefueling aircraft instead of the refueling drogue assembly 100. As withthe refueling drogue scenario, this outputted signal from the receiver300 is indicative of the discernable property carried on the opticalbeam that is received by the receiver 300 (except, of course, thereceiver 300 is located on the receiver aircraft 1105 or other airborneobject). Because the geometry of the scanning area 400 relative to theradiation emitter is known, the location of the receiver 300 within thescanning area 400 may thus be determined by comparing the discernableproperty of the received radiation to information stored in a look-uptable. Because the geometry of the receiver aircraft 1105 relative tothe receiver 300 is known, the position of the receiver aircraft 1105,in general, and a particular location on the receiver aircraft 1105(e.g., the end of the refueling boom 1111), relative to the radiationemitter may be determined.

Scanning

The operational characteristics of the radiation emitter 200 shall nowbe described. FIG. 4 depicts a side view of an exemplary embodiment ofthe radiation emitter 200 and receiver 300 arrangement. FIG. 4 is takenfrom the perspective view depicted in FIG. 1. FIG. 4 shows thatradiation emitter 200 emits a focused optical beam and moves that beamwithin lines 210 and 220. That is, from the side view of FIG. 4,radiation emitter 200 emits a beam in a scanning fashion such that thebeam moves within the area bounded by lines 210 and 220 so that thescanning area 400 may be scanned. By way of example only and not by wayof limitation, the radiation emitter 200 may emit a beam 202 at theorientation depicted in FIG. 4 at a time T₁, and then at a later timeT₂, emit a beam 204 at a different orientation from that of beam 202. Itis noted that in FIG. 4, the beam 202 is not intercepted by the receiver300, whereas the beam 204 is intercepted by the receiver 300. FIG. 5shows a top view of the radiation emitter 200 and the receiver 300depicted in FIG. 4. From FIG. 5, it can be seen that the radiationemitter 200 emits beams within the area bounded by line 230 and line240. Recognizing that FIG. 4 is a side view of the system and FIG. 5 isa top view of the system, a comparison of FIG. 4 with FIG. 5 shows thatthe volume (herein referred to as a scan zone and/or beam zone) boundedby lines 210 and 220 in FIG. 4 and lines 230 and 240 in FIG. 5 is in theshape of a cone, having its “top” located at the receiver 200. In theembodiment depicted in the Figs., the beam may be found within thisvolume/scan zone. In the embodiment depicted in FIGS. 4 and 5, the conehas a rectangular/square cross-section, as may be seen in FIG. 2. Thusthe scanning area 400 will be rectangular/square shaped. (However, otherembodiments of the present invention may utilize a circularcross-section or an oval shape cross-section. Indeed any shapedcross-section may be utilized as long as the goals of the presentinvention may be obtained.) It is noted that the exact geometry of thisscanning area may not be perfectly square/rectangular in view of thefact that the distance from the receiver 200 to the scanning areachanges with changing angular orientation of the beam with the radiationemitter 200. This phenomenon is discussed in greater detail below.However, for the present discussion, the scanning area will be treatedas a rectangular/square shape that is approximately normal to directionof beam travel away from the radiation emitter 200. It is further notedthat in many embodiments of the present invention, the beam will travelpassed the scanning area 400, if the beam is not intercepted by thereceiver 300. However, some embodiments of the present invention aresuch that the beam does not travel a significant distance beyond thereceiver 300 so that the beam may not be easily detected beyond closeproximity to the refueling aircraft 1000.

In a first embodiment of the invention, the radiation emitter 300 emitsa focused optical beam that is a focused optical elongated beam 210 andscans the beam over the scanning area, as may be seen in FIG. 6. FIG. 7shows the beam from the perspective of the scanning area, which isapproximately normal to the direction of travel of the beam. That is, ifthe scanning area was a flat surface, and the beam 210 impinged upon theflat surface, the beam would look approximately like that shown in FIG.7 when viewed in the direction of beam travel. In a first exemplaryembodiment, the radiation emitter 300 first scans the focused opticalelongated beam 210 over the scanning area starting from the top of thescanning area and ending at the bottom of the scanning area, inincrements, as may be seen, for example, in FIG. 8. (Note that in otherembodiments, the scanning may begin at the bottom and/or at the left orright sides (discussed below) and/or at any other location within thescanning area.) FIG. 8 shows, in a time-elapsed fashion, that at T₁, thebeam 210 is at a first position. At T₂, the beam 210 is moved to asecond position below T₁. At T₃, the beam 210 is moved to a thirdposition below T₂. Again, the beam depicted in FIGS. 6-8 show the resultof the focused optical beam as it would be if the beam impinges on thescanning area 400. FIG. 9 shows the focused optical beam impinging uponthe scanning area over times T₁ through T₁₃ in a time-elapsed manner.

After scanning from the top of the scanning area to the bottom of thescanning area, the radiation emitter changes the orientation of thefocused optical beam 210 from a horizontal orientation to a verticalorientation, as may be seen in FIG. 10. FIG. 11 shows the “impingement”of the beam 210 on the scanning area when the beam is elongated in thevertical direction. As may be seen in FIG. 12, radiation emitter 300scans the beam 210 over the scanning area 400 starting from left toright, in increments. That is, at time T₁₄, the elongated beam impingesupon the scanning area in the left-most position. At T₁₅, the beam ismoved from the left-most position to a position to the right. At T₁₆,the beam is again moved further to the right. FIG. 13 shows a timeelapsed view of beam impingement over the scanning area from time T₁₄ totime T₂₆.

Thus in comparing FIG. 13 with FIG. 9, it may be seen that the radiationemitter passes the beam over the scanning area in a two-pass or adual-pass manner: first from top to bottom, and then from left to right(or from left to right, and then from top to bottom, etc.)

Positioning Coordinate System

According to a first embodiment of the present invention, at least aportion of the scanning area 400 includes a positioning area 450, as maybe seen in FIGS. 14 and 15, in which the receiver 300 is likely to belocated. In this embodiment of the invention, this positioning area 450is entirely within the scanning area 400, as may be seen in FIG. 15, andthus the optical beam is scanned over the entire positioning area 450.However, in other embodiments, the boundaries of the positioning area450 may exceed the scanning area 400.

The airborne object positioning system is adapted to virtually divide atleast a portion of this positioning area 450 into a virtual grid 460.The virtual grid may include a plurality of distributed distinct sectorsthat spatially correspond to sub-areas within the positioning area. Thesub-areas are dispersed within the positioning area in a geometricallydefined manner. As may be seen in FIG. 15, receiver 300 of the airborneobject (e.g., refueling drogue assembly/refueling boom/receiveraircraft, etc.), during normal operation of the airborne objectpositioning system, is typically located within this positioning area,and thus the receiver 300 will receive radiation from the radiationemitter, during normal operational conditions, as the radiation passesover the receiver. FIG. 16 shows a focused optical elongated beam in thehorizontal position scanning over a row of distinct sectors/sub-areaswithin the virtual grid/positioning area 460/450. In a first embodimentof the present invention, the focused optical elongated beam scans fromtop to bottom in a continuous or in a step-wise manner, such that thefocused optical elongated beam is scanned over each row of distinctsectors/sub-areas. After scanning over all of the rows, the focusedoptical elongated beam is then focused to be elongated in the verticaldirection and is scanned over the positioning area, from column tocolumn, again either in a step-wise or a continuous manner (see FIG.17). As the optical beam moves from row to row and from column tocolumn, the discernable property of the beam changes in a manner thatmay be detected by the receiver 300. That is, were the receiver todetect a discernable property of the horizontal beam while in, forexample, the second row (that is, the discernable property correspondsto horizontal beam positioning within the second row), the radiationreceiver will be able to detect a different discernable property werethe beam and the receiver in the third row and so on. As noted above,the receiver is adapted to output a signal that is indicative of thediscernable property of the received radiation, to convey information tothe signal processor 500.

In an exemplary embodiment of the present invention, the grid 460 takesthe form of that presented in FIG. 55. Here, each grid line number isencoded into each line by modulating the laser beam as detailed herein.In this exemplary embodiment, the resolution at 1803 feet is 1 inch ofline spacing, and the grid generation rate is 20 Hz. It is noted that insome exemplary embodiments, the grid system operates in angularcoordinates/spherical coordinates/radial coordinates, etc. In some suchexemplary embodiments, line spacing is in units of angle, and the unitsof angle are converted to a linear distance through, for example, aradius, for human factors purposes (e.g., humans typically think interms of Cartesian coordinates, as opposed to angular coordinates). Byway of example and not by way of limitation, for high density linespacing, the system may convert between inches of resolution and deltaangle of resolution. Such may be done, for example, by dividing thenominal radius in inches. For example, referring to FIG. 55, delta thetawould equal 1 inch/21636 inches, which equals 0.00004621 rads. In someembodiments, the tangent and sine functions may be discounted becausethe angles are relatively small. Indeed, in some exemplary embodiments,the control system is such that there is no discernable differencebecause a control system utilizes an “error signal” algorithm, where theerror signal is driven to zero, and where the liner, sine and tangentfunctions all pass through zero.

Airborne Object (Receiver) Positioning

As noted above, the distributed distinct sectors of the positioning areacorrespond to sub-areas within the positioning area, the sub-areas beingdisbursed within the positioning area in a geometrically defined manner.This geometrically defined manner corresponds to a known orientation ofthe sub-areas with the radiation emitter 200. Therefore, the orientationof the virtual grid 460 with respect to the radiation emitter is known.By way of example and not by limitation, FIG. 18 shows that the centerof the grid 450 is located 100 feet behind and 10 feet below thereceiver 300. (The center of the grid 450 is centered with the radiationemitter 300—i.e. the “X” value is 0.)

Because the orientation of the scanning area/virtual grid with respectto the radiation emitter 300 is known, the discernable property of theoptical beam may be changed to correspond to the particular distinctsectors/sub-areas within the positioning area such that a uniquediscernable property may be carried on the optical beam for eachdistinct sector/sub-area. In this manner, the receiver 300, havingreceived the radiation from the radiation emitter 200 outputs the signalto the signal processor 500 indicative of the distinct property carriedon the optical beam received by the receiver 300, and thus, depending onthe discernable property of the received radiation received by thereceiver 300, by comparing the received discernable property to thosein, for example, a memory, the signal processor 500 can determine whichparticular distinct sector/sub-area the receiver was located in when thereceiver received the radiation.

The following is an exemplary scenario in which the airborne object100/1105 determines its position utilizing the first embodiment of theinvention. It is noted that by “determining its position,” it is meantthat in some instances, component(s) onboard the airborne objectdetermine the relative position of the airborne object to the receiveraircraft, in some instances a component(s) remote from the airborneobject (e.g., on the receiver aircraft 1000) determines the relativeposition of the airborne object to the receiver aircraft, and in someinstances both are the case. Indeed, some embodiments of the presentinvention are configured to simply transmit or otherwise conveyinformation regarding the radiation received by the radiation receiverfrom the receiver/airborne object to which the receiver is attached, tothe refueling aircraft, on which a processor 500 is located, so that theprocessor 500 may determine the relative location of the airborneobject.

Referring to FIGS. 19 and 20, receiver 300 is located within row 2 andcolumn 11 of the virtual grid 460. Radiation emitter 200 makes a firstpass over the scanning area, and thus the positioning area, with thefocused optical elongated beam, starting from the top of the scanningarea and moving to the bottom of the scanning area, moving the beam fromrow to row. The discernable property of the beam is changed as the beammoves from row to row. When the beam passes over/through row 2, thereceiver 300 detects radiation, and likewise detects the discernableproperty carried on the optical beam, the receiver 300 outputs a signalindicative of the discernable property of the received radiation tosignal processor 500 which determine that the discernable property isindicative of beam location in row 2. The radiation emitter 200continues to scan the beam over the scanning area. Once it reaches thebottom of the scanning area, the radiation emitter 200 then changes theorientation of the beam such that it is elongated in the verticaldirection and scans the scanning area from left to right, moving thebeam through each column in the virtual grid 460, changing thediscernable property carried on the optical beam as the beam moves fromcolumn to column. When the beam passes over column 11, the radiationreceiver receives radiation and outputs a signal indicative of thediscernable property carried on that received radiation. The signalprocessor 500 receives the signal and analyzes the signal to determinethat the discernable property is indicative of beam location in column11. The signal processor 500, remembering that the prior signal wasindicative of a beam position in row 2, recognizes that the receivermust be in column 11 and row 2 of virtual grid. (Note that in mayembodiments of the present invention, the two-pass scan takes placerelatively swiftly with respect to the dimensions of the virtual gridsuch that any movement of the airborne object/receiver during that timeis negligible.) Because the virtual grid corresponds to sub-areas of thepositioning area, by recognizing that the signal processor 500 receiveda signal indicative of beam location in the distinct sector of row 2 andthe distinct sector of column 11, and that these sectors correspond toone another, the signal processor 500 may determine the location of thereceiver within the positioning area, and thus determine the position ofthe receiver relative to the radiation emitter, because the position ofthe virtual grid relative to the radiation emitter is known.

FIG. 21 shows implementation of another embodiment of the presentinvention. Instead of utilizing a focused optical elongated beam in atwo-pass/two-scan manner, this embodiment utilizes a traditionalnon-elongated optical beam, as shown, such that when the beam impingeson the scanning area, the beam forms a circle as opposed to an elongatedline. In this embodiment, instead of scanning the beam in a two-passmanner over the scanning area, the radiation emitter 200 scans the beamin an X-Y raster over each of the individual discrete areas of thevirtual grid 450. In this embodiment, the discernable property carriedon the beam changes in a predetermined manner as the beam moves fromeach discrete area such that each discernable property is indicative ofa specific discrete area within the virtual grid corresponding to asub-area within the locating area. By way of example only and not by wayof limitation, in reference to FIG. 21, the radiation emitter 200 scansthe beam 280 across the virtual grid starting at block 1 (discretesector 1), moving the beam from block 1 to block 2, then to block 3,etc., over to block 13, and then moves the beam to block 14, and thenmoves the beam to block 15, block 16, etc., repeating this pattern untilthe beam has scanned over all of the blocks. This scan is thenautomatically repeated. In the scenario depicted in FIG. 21, when thebeam passes over box 24, the receiver 300 will receive the radiation,and thus the discernable property indicative of the beam when directedtowards box 24, and then output a signal indicative of the discernableproperty of received radiation to the signal processor 500. The signalprocessor 500 then determines that the radiation receiver is located inbox 24.

It is noted that in the above description of the X-Y raster, the beamwas moved from box 13 at the upper right side of the grid, all the wayon the left side of the grid. In another embodiment of the presentinvention, a raster scan may include, for example, moving the beam frombox 13 to box 26, after which the beam is moved to box 25, box 24, etc.,all the way to box 14, and then moved to box 27, and then to 28, andthen to 29, etc., all the way to 39, and then moved to box 52, and thento 51, etc. Thus, the raster scan includes both the traditional scanperformed by a cathode ray tube, as well as non traditional rasterscans. Other scanning patterns may be used as well.

It is noted that in the above-described embodiments, the beam scans overthe entire scanning area/virtual grid. Other embodiments of the presentinvention may be implemented where the beam only scans over a portion ofthe scanning area/virtual grid. By way of example only and not by way oflimitation, such may be the case in a system where the signal processor500 is in communication with the radiation emitter 200 such that afterthe processor 500 determines a general area within the grid in which thereceiver 300 is located, the radiation emitter 200 may concentrate thebeam on that general area, as opposed to over the entire area of thescanning area. That is, for example, if the signal processor 500continues to determine that the receiver is in box 24, or is in the areaof box 24, the radiation emitter 200 would not scan the area, say forexample, around box 121. However, if the signal processor 500 did notreceive a signal indicative of radiation within the area of box 24 forwithin a certain time period, the signal processor 500 may direct theradiation emitter 200 to again scan over the entire area so as toincrease the likelihood that the receiver 300 will receive radiation.This may also be done in the case of the focused optical elongated beammethod of scanning as well.

Airborne Object Position Control (Station-Keeping)

An embodiment of the present invention, utilizing the drogue positioningsystem detailed herein, to control the position of a refueling drogue,will now be described by way of an exemplary scenario. As a preliminarymatter, it is noted that drogue control may be implemented according tothe teachings of U.S. patent application Ser. No. 10/697,564 filed onOct. 31, 2003, entitled Stabilization of a Drogue Body, the contents ofwhich are incorporated herein in their entirety. U.S. patent applicationSer. No. 10/697,564 claims priority to U.S. Provisional Application Ser.No. 60/498,641 filed on Aug. 29, 2003, the contents of which are alsoincorporated by reference herein in their entirety, the teachings ofwhich may also be used to control the position of a refueling drogue.Further, it is noted that the drogue utilized in particular and/ordrogue control in general may be implemented according to the teachingsof Patent Cooperation Treaty Application PCT/US2006/049258 filed on Dec.22, 2006, entitled Controllable Drogue, the contents of which areincorporated herein in their entirety. PCT Application NumberPCT/US2006/049258 claims priority to U.S. Provisional Patent ApplicationSer. No. 60/752,380 to Mike Feldman, entitled Controllable Drogue, filedon Dec. 22, 2005, the contents of which are incorporated herein in theirentirety.

Initially, the drogue 100 is extended from a drogue carrier attached toa wing of an aircraft 1000. The drogue assembly 100 will be extended asufficient distance from the aircraft 1000 so that aerial refueling maybe conducted. This distance, in an exemplary embodiment, is about 100feet from the wing (and thus the radiation emitter), although in otherembodiments, this distance may differ based on the local conditionsand/or the type of mission required for the aerial refueling. Therefueling drogue assembly 100 will be permitted to obtain a nominalposition/effectively constant position (a constant position the locationof which will vary with different atmospheric conditions, aircraftspeed, etc.) with respect to the aircraft 1000, and thus the radiationemitter 200. At this time, according to this scenario, the aircraft tobe refueled is a sufficient distance away from the refueling drogueassembly 100 such that the aircraft to be refueled does not impart anyforces onto the drogue that may cause the drogue's position to move.

As noted above, wind gusts, turbulence, the receiver aircraft, etc., mayimpart forces on the drogue assembly 100 that will make the drogue movefrom its “effectively constant position.” Based on empirical and/oranalytical analysis, it is known that, for example, under the given setof circumstances for a particular refueling mission, the position of thedrogue/receiver may be maintained within about a 6 inch radius of anominal location, in some embodiments, within about 2-3 inches, and inothers even smaller, such as about 1-2 inches and/or even less than aninch. In some embodiments, the system accounts for turbulence in thefrequency range of 1-3 Hz that can cause a few feet of droguedisplacement. Moreover, in some embodiments of the invention, thestabilization system may account for bow wave (from the receivingaircraft), which induces translation. Specifically, the system mayaccount for bow wave of steady state that can cause about five feet ofdisplacement and/or 2 to three feet of displacement, depending on suchvariables as, for example, the control surface size, control surfacedeflection, control surface actuator force, etc, of the drogue activecontrol system. Some embodiments of the present invention may beimplemented to account for forces that cause the drogue to move as muchas 10 feet in any direction from a “nominal position” relative to theradiation emitter 200. (For other missions, the drogue could move moreor less.) Accordingly, for this particular mission, the area of likelymovement of the drogue, i.e., this “10 feet in any direction,” willdefine the scanning area 400 in a first embodiment. That is, thegeometry of the scanning area 400 will be set to be 20 feet by 20 feet,centered about the nominal position of the drogue, such that thereceiver 300 is very likely to be located within that area during anormal refueling operation. (For other missions, the area may be 10 feetby 10 feet, 10 feet by 20 feet, or more or less, depending on theconditions of the mission. If refueling is being conducted duringrelatively calm atmospheric conditions, the scanning area would likelybe smaller than a scanning area for un-calm conditions.)

It is noted that the location of the scanning area 400 may be adjustedbased on the nominal location of the drogue assembly. That is, forexample, referring to FIG. 1, for a first type of refueling mission, thenominal location of the drogue may be located, on average, 105 feet inthe Z direction, and minus 5 feet in the Y direction, from the radiationemitter 200. In a second type of refueling mission, the drogue mayinstead nominally be 90 feet from the radiation emitter 200 in the Zdirection, and be negative 15 feet in the Y direction from radiationemitter 200.

It is noted that in some embodiments of the invention, the droguepositioning system is configured to adjust the location of the scanningarea to conform to the location of the receiver 300. By way of example,the radiation emitter 200 may move the scanning area over a wide area toinitially find the nominal location of the drogue, and then refine thescanning area about the drogue. It is noted that in other embodiments ofthe invention, the drogue positioning system may instead simply startoff with a very large scanning area such that the beam may be moredispersed, such as in the instance of use of a focused optical elongatedbeam, thus covering a greater area. Upon identification of the nominallocation of the drogue/receiver, the scanning area may be narrowedaccordingly.

In other embodiments of the present invention, the refueling aircraftmay include a device that detects the nominal location of the drogue,and uses this detection to direct the scanning area. In otherembodiments of the invention, an operator on-board the aircraft 1000directs the scanning area at the drogue.

It is also noted that in some embodiments of the present invention, itis not necessary that the scanning area be centered on the nominallocation of the refueling drogue. Such may be the case in conditionssuch that it is expected that the drogue will move from the nominallocation in some directions more than in other directions.

Once the drogue is nominally located, and the scanning area is directedto this location, the positioning system may begin operating to identifythe position of the drogue within the scanning area. Assuming a virtualgrid having 13 columns and 13 rows, as is exemplarily depicted in FIG.14, if the nominal position of the refueling drogue is known, thescanning area/grid will be positioned such that column 7 and row 7 arepositioned at the nominal location of the refueling drogue. As discussedabove, the radiation emitter 200 may scan over the scanning area, andthus over the virtual grid. The signal processor 500 will determinewhere the receiver/drogue assembly is located within the grid based onthe radiation received by the receiver 300 while the radiation emitter200 scans the scanning area. In this exemplary scenario, if the signalprocessor 500 determines that the drogue/receiver 300 is still locatedat virtual row 7, column 7, the active control system of the drogueassembly will not change its position. However, if, for example, thesignal processor 500 determines that the drogue has moved within thevirtual grid to row 6, column 7, the signal processor 500 will output asignal to the active control system to move the drogue downward (i.e.,in the negative Y direction). The active control system may be commandedto move the drogue downward until the receiver again receives radiationfrom the signal processor that the drogue/receiver is again located atits nominal position. If, for example, the radiation is indicative ofreceiver position in row 7, column 7, the signal processor will tell theactive control system to stop directing the drogue downward. However, iffor example the signal processor determines that the drogue is now atrow 8, column 7, this signal processor will output a signal to theactive control system to direct the drogue upwards, (i.e., in thepositive Y direction). Thus, the drogue positioning system may beutilized in an iterative manner to control drogue location. It is notedthat other embodiments of the present invention may operate in differentmanner. That is, for example, if there is a repeating tendency for thedrogue to move from row 7, column 7 to, for example, row 6, column 7,the active control system may adjust a trim on some of the controlsurfaces of the drogue assembly to direct the drogue back to row 7,column 7, such that this tendency is negated. Basically, the droguepositioning system may be used in any manner that will enable theposition of the drogue to be determined such that the position may beadjusted/controlled utilizing an active control system.

It is noted that in some embodiments of the present invention, thedistal portion of the refueling hose will be the portion of the drogueassembly that is actively controlled. This is because in someembodiments, the drogue assembly 100 may include a flexible joint, whichmay be located between the hose 110 and the drogue 105, allowing thedrogue 105 to pivot about the centerline of the hose (see, FIG. 3). Insuch embodiments, it is typically the position of the distal end of thehose that is controlled. In other embodiments, typically, where the hoseis rigidly connected to the drogue 105, it is the position of the drogue105 that is controlled. Accordingly, in some embodiments of theinvention, the receiver is rigidly connected either directly to or byway of a rigid interface to the controlled component. If the position ofthe hose is to be controlled, the receiver will typically be rigidlyconnected to the hose, as may be seen, for example, by FIG. 3. It isnoted that some embodiments of the present invention extend to aretrofit kit including an adapter on which a receiver is mounted thatcouples a drogue 105 to a hose 110. Depending on which component is tobe controlled, the adapter is rigidly connected to that component. Insum, by reference to controlling the location of a refueling drogueassembly, it is meant that at least one point on/in the refueling drogueassembly (drogue, distal portion of the hose, adapter, etc.) iscontrolled, recognizing that other parts of the drogue assembly may notbe controlled.

It is noted that while the just-described scenario is detailed in termsof controlling the position of a refueling drogue, the scenario isreadily applicable to controlling the position of a host of otherairborne objects, such as, for example, a refueling boom, a receiveraircraft (or a plurality of receiver aircraft), including autonomousdrones, etc. Accordingly, embodiments of the present invention includeany device, system, method and/or algorithm which permits some or all ofthe above-discussed actions to be undertaken with a variety of airborneobjects including receiver aircraft, etc.

Embodiments of the present invention may be practiced in accordance withthe teachings herein to enhance aerial refueling by directing one orboth of an aerial refueling device and a receiver aircraft, based on therelative positioning information obtainable according to the teachingsherein, to mate with one another. That is, the relative positioninginformation obtainable according to the teachings herein may be used to“fly” (in some embodiments, automatically) a refueling drogue (orrefueling boom) to a receiver aircraft, fly a receiver aircraft to arefueling drogue, and/or do both, automatically. Accordingly,embodiments of the present invention include devices, systems, methodsand algorithms for use in mating (in some embodiments, automatic mating)of one airborne object with another airborne object.

Specific Features of Some Embodiments

Specific features of the airborne object positioning system will now bediscussed.

As noted above, the radiation emitter 200 may output a focus opticalbeam. It will be noted that other embodiments of the present inventionmay utilize other types of radiation. Basically, any type of radiationthat may be utilized to determine the airborne object location accordingto the present invention may be used. By way of example only and not byway of limitation, electromagnetic radiation may be utilized. Such anembodiment may utilize technologies associated with VOR and ILS. Asnoted above, the radiation emitter emits radiation that carries adiscernable property that may be received by a receiver and analyzed.This discernable property is used as a reference by the signal processor200 to determine the location of the receiver/airborne object within thevirtual grid and the positioning area. This discernable property, insome exemplary embodiments, is created by modulating the beam withdigital data blocks that represent the current location of the beam inthe scanned area/positioning area. An example of a digital data blockmay be seen in FIG. 22. FIG. 22 shows a schematic drawing of amodulation of a projected beam. In FIG. 22, a block is exploded. By wayof example, only, this block represents a 20-bit data block typical ofthe other blocks. In this block, the first 8 bits are headerinformation, while the remaining 12 bits represents informationregarding the row or column at which the focused beam is directed. FIG.22 shows that the block is 0.25 inches in length. This corresponds tothe width or height of a column or row, respectively, at the trackingarea. That is, as the beam scans over the area, the beam is modulatedsuch that modulation sufficient to indicate a column or row is completedas the beam moves 0.25 inches in the area. For example, the first 0.1inch of movement corresponds to header information, while the last 0.15inches of movement corresponds to the row/column information. Thus, inthis embodiment, the modulation is substantially continuous. (Althoughin other embodiments, the modulation need not be continuous.) Because insome embodiments the processor 500 is configured to recognize a header,the processor may thus determine that the received radiation isindicative of a new row or column once a new header is received. It isnoted that in other embodiments of the present invention, a 24 bit worddata block is utilized, where 20 bits are used for positioning, and thespare bits may be used for other informational purposes such as, forexample, data link of commanded positions, etc. The approximate data bitrate in an exemplary embodiment is 26 Mhz.

In some embodiments of the present invention, modulation is obtained bycycling the intensity of the beam, which in some embodiments correspondsto shutting the beam off (or otherwise blocking the beam) and thenturning the beam on (or otherwise directing the beam to the area). Otherembodiments may utilize multiple intensities. Embodiments of the presentinvention may utilize standard digital modulation techniques, such asthose utilized in encryption, if those modulation techniques may becoupled to beam location/direction.

It is also noted that the discernable property of the beam may be uniqueto a given column and row. That is, every column and every row,collectively, may have different discernable properties associated withthat column/row. For example, column 2 will be associated with adiscernable property that is distinct with all the other discernableproperties for all other columns and rows. Such may be accomplished, forexample, by utilizing a “smart header:” a header that includesinformation pertaining to whether the beam is aligned horizontally orvertically, but still allows for the processor to determine that a newblock is being transmitted (discussed more below). However, otherembodiments of the present invention may utilize the same discernableproperties between columns and rows. For example, column 1 may becorrelated to a discernable property that is the same as that for row 1,row 2, or row 3, etc. However, in such a situation, based only on thediscernable property, without more, the system would not know whetherthe discernable property is indicative of a column position or a rowposition. In such instances, for example, the timing between the firstand the second pass of the two-pass scan may be adjusted such that everyfirst receipt of radiation is a scan from top to bottom (e.g., a scanindicating row position), and every second receipt of radiation is ascan from left to right (e.g., a scan indicating column position), or inany other pre-determined pattern. Such may be determined, by way ofexample, by pausing in-between each scan for a certain amount of time.For example, a scan from top to bottom might be separated by apredetermined time period from the following scan from left to right.The scan from left to right may in turn be separated by differentpredetermined time period. The signal processor 500 may be programmed tolook for different time periods between receipt of outputted signalsfrom the receiver and, from a look-up table, recognize the type of scan.Alternatively, the beam may carry two or more discernable properties atthe same time. For example, one property may be indicative of the typeof scan (either top/down or left/right) and the other may be indicativeof the location within the scan area, i.e., what column/row).

By way of additional example, in the case of utilizing a non-elongated(normal beam) such is shown in FIG. 21, one discernable property may beadjusted to indicate the beam's location within a column, while theother discernable property may be adjusted to indicate the beam'slocation within a row such may be used for two-pass scans as well. Insummary, any type of modulation/change in discernable property ofradiation that may be utilized to correlate beam location within thevirtual grid with respect to the radiation emitter may be utilized topractice the present invention.

It is noted that beam receiver overlap may be utilized to practice thepresent invention. That is, by way of example, some embodiments of thepresent invention may utilize a ratio of 6 to 1 for beam/receiveroverlap, although other embodiments may utilize a larger or smallerratio. Overlap may be obtained by utilizing either a big beam/smallreceiver, or a small beam/big receiver. FIG. 23 shows an exemplaryscenario utilizing an embodiment utilizing a big receiver/small beam. InFIG. 23, the rows (and although not shown, the columns) of the virtualgrid are such that multiple rows (and columns) fit within the receiveraperture when virtually overlaid with the receiver aperture. In theembodiment shown in FIG. 23, 7 rows fully fit within the receiveraperture, although again, more or less rows may be utilized in otherembodiments. In an embodiment according to FIG. 23, the discernableproperty may change at least seven times as the beam moves through eachof the rows, and thus the receiver may output seven signals, each ofwhich indicate a specific discernable signal. This will be, of course,the case for the columns of the grid as well, providing that the columnsare dimensioned similar to the rows of the grid. In this regard, columnsize and row size may be directly correlated to the ability to controlthe beam and to vary the discernable property of the beam.

In a first embodiment of the present invention, it is expected that thecolumns and rows of the virtual grid will be 0.25 inches in height/widthwhen the scan area is about 100 feet from the radiation emitter andabout 10 feet below the radiation emitter. Thus, the discernableproperty of the beam may change as the beam moves 0.25 inches in thesweeping direction. Of course, other embodiments of the presentinvention may use a larger or smaller row/column height/width. By way ofexample, some embodiments may utilize heights/widths of 0.1 inches orless and/or 1.0 inches or more. In many embodiments of the presentinvention, the discernable property of the beam will change as it movesfrom one column to the other. Thus, the discernable property may changeless frequently for grids utilizing rows and columns that are larger.According to some embodiments of the invention, the scan area will be a120 inch×120 inch square, at 100 feet from the radiation receiver, andthe row/column height/width will be 0.25 inches. Thus, the scan areawill be made up of 480×480 columns and rows (scan lines). However, itwill be noted that other embodiments of the present invention may usedifferent sized/shaped scan areas. By way of example only, and not byway of limitation, a circular scan area may be used where the beam isscanned in a helical pattern, starting from the center and movingoutward. In such an embodiment, again, it may be possible to have aninteractive system such that the scan begins at the center, wherereceiver is most likely to be located, and then scans outward, and oncethe radiation receiver receives the radiation, the radiation emitter maybe controlled to reset the scan again, starting at the center and/or atthe approximate location of the airborne object. Other embodiments mayutilize a rectangular section or any other shaped section that willachieve the results of airborne object positioning, according to thepresent invention.

In the example of FIG. 23, where the height of each row represents 0.25inches, the receiver will receive fully seven different discernableproperties carried on the received radiation, and output seven differentsignals to the radiation receiver, (or alternatively, output a singlesignal carrying a data package which is indicative of the sevenindicative properties received by the received radiation). In otherembodiments, the receiver simply outputs signals indicative of allinformation received, and lets the signal processor 500 determinewhether a full data set has been received. The signal processor 500 willanalyze the signal(s) and determine that radiation has been receivedthat is indicative of seven different rows within the grid, and thus theexact position within the virtual grid may not necessarily be known. Insome embodiments, the receiver and/or signal processor determine whethera full data set has been received base on the number of bits receivedbetween receipt of headers. For example, in the scenario depicted inFIG. 23, the receiver will not receive a header until row 2, and thuswill know to ignore the information preceding. Also, after receiving theheader of row 9, the receiver will not receive another header, and alsowill not receive a full 20 bits of information before the radiationstops, and thus will know to ignore any information following the lastreceipt of 20 bits. In such a scenario, the receiver and/or signalprocess such that the seven different rows are averaged in a manner suchthat the average row location would be determined. For example, in thefigure of FIG. 23, the average row will be row 5. If, for example, thereceiver aperture was moved downward 1 row such that the average row wasrow 6, the signal processor could output a signal to the activecontroller to adjust the control to move the airborne object upward,such that the average of the received rows would again be row 5. Stillfurther, referring to FIG. 23, it may be seen that radiation from row 1and radiation from row 9 would also be received by the receiver, if onlyin a fractional amount. According to an embodiment of the invention,this partial received radiation may correspond to only a receipt of apartial data set, and the receiver may be of a design such that thereceiver will not output a signal upon receipt of only a partial dataset/partial amount of radiation. That is, with reference to FIG. 23, thereceiver would only out put seven signals, not nine signals (i.e., thereceiver would basically ignore the radiation of column 1 and column 9.However, other embodiments of the present invention may output a signalupon even receipt of a partial data set.

In another embodiment of the invention, the number of bits receivedduring a pass is used to obtain a hyper accurate position within asector/sub-area. Referring to FIG. 23, the processor 500 know the numberof bits that it received, and know that it received a full data set forlines 2 through lines 8. For example, the processor 500 will know thatit received 7×20 bits for rows 2 through 8, that it received, forexample, 5 bits before it received a full 20 bits representing row 2,and that it received 10 bits after it received a full 20 bitsrepresenting row 8. The processor can thus determine that the center ofthe receiver is located closer to row 9 than row 1. In fact, theprocessor can determine that the center of the receiver is about 12.5bits away from the top of row 5 (e.g., 155 bits received, divided by 2,minus the 5 bits received from line 1=72.5 bits below the top of line 2,and if each line represents 20 bits, the center will be 12.5 bits awayfrom the top of row 5—the distance from the bottom of row 5 may bedetermined as well, both to verify the correctness of the calculation,or to smooth possible rounding errors.) Thus, instead of simply beingable to determine that the receiver is centered within row 5, adetermination may be made that the receiver is centered 0.15625 inchesbelow the top of row 5 (12.5 bits divided by 20 bits times 0.25 inches).Other algebraic manipulations may be utilized as well to practice thisembodiment of the invention to obtain hyper accurate results.

A processing algorithm that may be used in the present invention is asfollows. Assuming that the raster is numbered top down and that themessage packets are numbered left to right, the center raster scan lineis:

-   -   A.        Lowest_number_scan_line_detected+((Highest_number_scan_line_detected−Lowest_number_scan_line_detected)/2).    -   B. The center packet is: For the scan line from “A,” above,        lowest_packet        number+((highest_packet_number−lowest_packet_number)/2).

As noted above, embodiments of the present invention may either utilizebig beam/small receiver or a small beam/big receiver. Any size beam andany size receiver may be utilized providing that airborne objectpositioning may be obtained according to the present invention.

Many of the embodiments, according to the present invention utilize thevirtual grid as detailed above. However, other embodiments of thepresent invention may be practiced without utilizing a virtual grid. Byway of example, a focused optical non-elongated beam, such as thataccording to FIG. 21, may be scanned such that the beam containsdiscernable properties that are indicative of the angular orientation ofthe beam with respect to the radiation emitter. In such a situation, tworeference planes may be created, which may be, but do not necessarilyhave to be orthogonal to one another. For example, FIGS. 24 and 25 showangular orientation from planes extending out of the view passingthrough the nominal angle of beam direction as may be seen. According toFIG. 24, the receiver is located at plus 10 degrees above the planepassing through the nominal angle. According to FIG. 25, the receiver islocated at plus 5 degrees to the side of the plane passing through thenominal angle. If the nominal “location” of the beam is plus 10 degreesand 0 degrees, the active control system may be directed to steer theairborne object back 5 degrees. In such an embodiment, both theelongated beam and the non-elongated beam method of scanning may beused. If the non-elongated beam method is used, the beam zone, the beamzone may include a plurality of distributed distinct vector of knownorientation with the radiation emitter such that if the signal processordetermines which distinct vector a received beam coincides with, theorientation of the receiver relative to the radiation emitter may thusbe determined. That is, the distinct vectors correspond to actualorientations of the beam with respect to the radiation emitter, theactual orientations being disbursed within the beam zone in ageometrically defined manner.

In such an embodiment, the radiation emitter is adapted to direct a beamof emitted radiation to an area away from the radiation emitter, theradiation including discernable properties that vary in a correspondingmanner with varying orientation of the beam of radiation with respect tothe radiation emitter. By way of example, the radiation emitter isadapted to emit a focused optical beam modulated with digital datablocks, the modulated digital data blocks respectively indicative ofdiscrete orientations respectively corresponding to orientations of thebeam relative to the radiation emitter. Some of the varied discernableproperties are respectively indicative of discrete orientationsrespectively corresponding to orientations of the beam relative to theradiation emitter in a first reference frame, and wherein at least someof the varied discernable properties are respectively indicative ofdiscrete orientations respectively corresponding to orientations of thebeam relative to the radiation emitter in a second reference frame.

Based on the output of the receiver, the processor is adapted to processthe outputted signal and identify a first virtual orientation indicativeof an orientation of the receiver relative to the radiation emitter whenat least a portion of the radiation was received by the receiver. By wayof example, the signal processor is adapted to analyze a first outputtedsignal from the receiver that is indicative of a first discernableproperty of the received radiation indicative of a first discreteorientation corresponding to a first orientation of the beam relative tothe radiation emitter in the first reference frame at the time that theradiation was received. Still further by way of example, the signalprocessor is adapted to analyze a second outputted signal from thereceiver, the second outputted signal being indicative of a seconddiscernable property of the received radiation indicative of a seconddiscrete orientation corresponding to a second orientation of the beamrelative to the radiation emitter in the second reference frame at thetime that the radiation was received. Accordingly, the signal processoris adapted to identify a virtual location of the receiver relative tothe radiation emitter based on the analysis of the first and secondoutputted signals.

As discussed above, some embodiments of the present invention areconfigured to permit the airborne object 100/1105 to maintain a positionrelative to the radiation emitter. Such maintenance may be performed insome embodiments without the need for communication between theradiation emitter and the airborne object 100/1105. For example, thesignal processor 500 on the airborne object 100/1105 may be furnishedwith look-up tables sufficient to analyze the signals from the receiverand identify the current location of the refueling drogue within thepositioning area/virtual grid. However, in other embodiments, theairborne object may be in communication with the refueling aircraft1000, or other location remote from the airborne object. In suchembodiments, a simple communications link may be established from thereceiver 300 and/or the processor 500 to components onboard the aircraft1000. Indeed, in some embodiments, position determination is determinedat a location remote from the airborne object, the airborne objectmerely communicating information about the received radiation sufficientfor the remote location to evaluate the relative position of theairborne object.

FIG. 60 presents a high level exemplary control algorithm usable in thetarget (e.g., a refueling drogue) for evaluating position of the targetwith in the grid(s).

An embodiment of the prevent invention include kits that comprisedevices that will enable conventional refueling drogue or other airborneobject to be retrofitted for positioning determination and/or to beactively controlled. (Such embodiments also extend to methods ofconversion as well.) Such devices might come in the form of a pack thatincludes a receiver, a signal processor, and/or control surfaces,sensors, etc., necessary to implement positioning determination and/oractive control. In some embodiments of the present invention, a pack mayhave the positioning system and the active control system in one pack,or at least the components that physically interface with the air stream(e.g., the vanes, the control surfaces, etc.) required to implementthose systems (the other components may be added directly to therefueling aircraft as long as there is a means to interface with theretrofit packs). Thus, any kit/pack that contains any or all of theabove elements of the airborne object positioning system and/or theactive control system and/or will permit the implementation of thefunctions of position determination and/or active control on an existingrefueling drogue or other airborne object, may be utilized to practicesome embodiments of the invention

It is further noted that the present invention includes software,firmware and/or computers (including simple logic and/or error circuits)adapted to implement the above techniques. Also, while some embodimentsof the present invention may be practiced manually, other embodimentsmay be practiced automatically. Thus, the present invention includes anydevice or system that may be configured or otherwise used to implementthe present invention in an automated manner.

Some embodiments of the present invention may be configured to generateelectricity at the refueling drogue 100, to power the receiver, thesignal processor and/or the active control system, etc.

As discussed above, the scanning area is treated as being an area thatis flat. However, under such treatment, the distance of the scanningarea to the radiation emitter will be larger at the edges of thescanning area than at the center of the scanning area (assuming ascanning area centered about the nominal direction of the emitted beam),owing to the change in angle of the beam between the center and theedges of the area. Thus, the distinct sectors of the virtualgrid/sub-areas may differ in size between those at the center of thegrid/locating area and those at the edges to account for thisphenomenon. Indeed, in some embodiments of the invention, the grids aredefined by the optical beam. That is, how the beam changes controls thesize and shape of the virtual grid/the sub areas. In this respect, thegrid is more of a convenient way to express location of the airborneobject. If the present invention is practiced to maintain a position ofthe airborne object, uniformity of the virtual grid is not needed. Infact, the grid could be dispensed with entirely, providing that logic isutilized to control the position of the airborne object. (For example,large look-up tables may be utilized and/or modified fly-by-wire logicmay be used corresponding to the various discernable properties as theycorrespond to orientation of the beam with the radiation emitter. Forexample, exhaustive if-then routines might be utilized.) Alternatively,the angular change of the orientation of the emitted beam may be variedto utilize a consistently sized grid (i.e., larger angular changes whilescanning at the edges of the grid/tracking area than while scanning nearthe center of the grid. Also, a combination of the two may be utilized.

In this regard, the tracking area/virtual grid may be treated as acurved surface instead of a flat area. In this regard, it is noted thatwhen the airborne object 100/1105 moves relative to the radiationemitter, it is likely that the airborne object 100/1105 will move inthree dimensions. That is, assuming that the refueling hose 110 is of aconstant length during refueling, a change in position in the “X” or “Y”direction (referring to FIGS. 1 and 2) will result in a change inposition in the “Z” direction. Thus, embodiments of the presentinvention may be implemented that account for the position of theairborne object in three dimensions (i.e., a positioning volume may beutilized to determine the position of the airborne object). Such may beaccomplished by adding, for example, a second radiation emitter or asecond radiation receiver a know distance from the first radiationemitter or the first radiation receiver, respectively, and triangulatingbetween the two. Alternatively or in addition to this, some embodimentsof the present invention might utilize two or more receivers spacedabout the airborne object that analyze which beam was received by whichreceiver during a given pass. For example, if at a distance of 100 feetfrom the radiation emitter, for a given location within the receivingarea, receiver A is expected to receive radiation carrying a propertyindicative of receiver position at column 45 and receiver B is expectedto receive radiation carrying a property indicative of receiver positionat column 57, and if at a distance of 102 feet from the radiationemitter, again for the “same” location within the receiving areareceiver A is expected to receive radiation carrying a propertyindicative of receiver position at column 44 and receiver B is expectedto receive radiation carrying a property indicative of receiver positionat column 58, the distance in the “Z” location may be obtained based onthis phenomenon, as applicable.

As just detailed, embodiments of the present invention may utilize twoor more radiation emitters 200. In such a scenario, when utilizingradiation emitters that have the same field of view (discussed ingreater detail below), the total scanned area may be increased by afactor of 2 or more. For example, if a first radiation emitter has afield of view of 45 degrees, and the second radiation emitter has afield of view of 45 degrees, a combined field of view of 90 degrees maybe obtained (three such emitters might yield 135 degrees, etc.). In someembodiments, the fields of view may be interleaved such that the tworadiation emitters overlap a single scan area. (See FIG. 58 for anexemplary scenario of two radiation emitters with a 45 degree field ofview overlapping each other.) In embodiments of the present inventionwhere respective scan areas of radiation emitters overlap one another,redundancy is achieved in the overlap area (depending on the extent ofthe overlap, a larger field of view may be achieved as well, as isdepicted in FIG. 58.) Further, data may be obtained from the overlap foruse in fault detection routines. Also, overlap may be set up to beweighted in the “X” direction, the “Y” direction, or may be weightedsymmetrically with respect to both directions. Some embodiments of thepresent invention are configured to vary the fields of view/thedirections of the fields of view of the radiation emitters duringoperation. That is, some embodiments of the present invention areconfigured to “steer” the fields of view towards areas of interest withrespect to the aircraft 1000. Any device, method, algorithm and/orcontrol system that will permit scan areas to overlap may be utilized topractice some embodiments of the present invention.

Also as just detailed, embodiments of the present invention may utilizetwo or more receivers 300. This may be done, for example, in a scenariowhere roll attitude determination of a target (e.g., the drogue, thereceiver aircraft, etc.) is desired. In other embodiments, the multiplereceivers may be arrayed on respective multiple targets/airborneobjects. By way of example, a plurality of receivers may be arrayed on aplurality of receiver aircraft 1105, respectively, and the plurality ofreceiver aircraft may be tracked. That is, in this exemplary embodiment,multiple receiver aircraft may be optically tracked by a single aircraft1000 and/or tracked at a location remote from the aircraft 1000 and themultiple receiver aircraft. In such embodiments, one or more emitters200 may be utilized (e.g., as detailed herein, multiple emitters 200 maybe utilized to expand the scanned area), although in some embodiments, asingle emitter 200 may be utilized providing that it provides a largeenough field of view for the multiple targets to be in the field of view(e.g., sufficient room for maneuvering, etc.). It is noted that in someembodiments of the present invention, a first target may be relativelyclose to the emitter 200 (such as, for example, during the finalapproach towards a refueling drogue/boom, while a second target may berelatively far from the emitter 200, thus providing sufficient “room’for the two targets to maneuver).

Accordingly, in an exemplary scenario utilizing the present invention,two or more airborne objects are positioned proximate the refuelingaircraft, each having at least one radiation receiver, respectively. Thereceivers respectively receive the laser beam(s) emitted from one ormore radiation emitters onboard the refueling aircraft 1000, and themodulation of signal(s) carried on the received laser beam(s) isanalyzed to determine respective positions of the receivers (and thusthe position of the respective airborne objects). Accordingly, therelative position of a plurality of airborne objects may be determinedsimultaneously. It is again noted that as with a single airborne object,the receiver aircraft (or other remote location from the airborneobjects) may be configured to receive information indicative of thelocation of the airborne objects (e.g., true positioning coordinates,information pertaining to the radiation received by the respectivereceivers onboard the airborne objects, etc.) transmitted to thereceiver aircraft (or other location remote from the airborne objects).Such a scenario will likely be practiced in the event that the airborneobjects are drones.

In yet other embodiments, especially those relating to determining therelative location of a receiver aircraft/a component on the receiveraircraft, the “Z” location of the receiver 300 may be determined byconfiguring the receiver 300 with an aperture of known size so thatrange information may be extracted based on the number of scan linesthat pass through the aperture during a Y sweep and/or an X sweep and/orboth. In this regard, referring to FIG. 49, where each scan linerepresents a single cycle of the “data clock” that is imposed on thelaser beam, for a constant aperture size, it may be seen that there willbe more scan lines (and therefore more clock cycles) within the field ofview of the aperture as the aperture moves closer to the radiationemitter 200 (note the number of lines that pass through the aperture at“Range_B” as compared to “Range_A,” the latter being more distant fromthe emitter 200 than the former). In some embodiments, the number oflines (or clock cycles, as is detailed herein) that pass through theaperture to be received by a detector in the receiver 300 is nonlinearlyproportional to the distance from which the receiver 300 is located fromthe radiation emitter 200. Accordingly, an exemplary embodiment of thepresent invention includes a system adapted to extract information fromthe radiation emitted from the radiation emitter which is received bythe radiation receiver indicative of a straight-line distance betweenthe radiation emitter and the radiation receiver. In an exemplaryembodiment, the extracted information is based on the amount ofradiation received by the radiation receiver during a predeterminedperiod of time, and the system includes an algorithm having theparameters such that the more radiation that is received by theradiation emitter during the predetermined period of time, the smallerthe straight-line distance between the radiation emitter and theradiation receiver. In some embodiments, the system is configured suchthat the radiation emitter modulates an intensity of the beam accordingto a periodic cycle. The system is configured to extract informationfrom the radiation emitted from the radiation emitter which is receivedby the radiation receiver indicative of a straight-line distance betweenthe radiation emitter and the radiation receiver. This information maybe based on the number of modulations detected by the radiation receiverduring a predetermined period of time. The system may include analgorithm having the parameters such that the greater the collectiveintensity of radiation that is received by the radiation emitter duringthe predetermined period of time, the smaller the straight-line distancebetween the radiation emitter and the radiation receiver.

In yet other embodiments, the radiation emitter cycles emission of thebeam (i.e., turns the beam on and off) according to a periodic cycle todirect a plurality of lines towards the radiation receiver. The systemis adapted to extract information from the radiation emitted from theradiation emitter which is received by the radiation receiver indicativeof a straight-line distance between the radiation emitter and theradiation receiver—the information being based on the number of emissioncycles detected by the radiation receiver during a predetermined periodof time. Also, the system includes an algorithm having parameters suchthat the higher number of emission cycles that are received by theradiation emitter during the predetermined period of time, the smallerthe straight-line distance between the radiation emitter and theradiation receiver.

In some embodiments of the present invention, the receiver 300 includesa laser detector configured to receive the radiation (e.g., the laserbeam) emitted from the radiation emitter 200. In an exemplaryembodiment, the receiver 300 is in the form of an assembly thatcorresponds to the conceptual diagram presented on FIG. 48, with, by wayof example, the serial communication being with processor 500. Thereceiver 300 may include biasing, threshold detection, AGC and/oradaptive threshold and/or gain control and digitizing electroniccomponents. The receiver 300 may be configured to permit locationdetection in three dimensions. In an exemplary embodiment, the size ofthe aperture of the receiver 300 is such that three scan lines cross thedetector (which is depicted as a diode detector) in FIG. 48 at themaximum usable range of the system. In some embodiments, it issufficient that the aperture be configured such that a full single scanline will cross the detector.

According to the above, embodiments of the present invention may beimplemented utilizing positioning areas and/or positioning volumes in amanner that will permit drogue positioning/station keeping to beimplemented according to the present invention. In summary, anycoordinate system may be utilized to practice the present invention.

Scaled Test Model

U.S. Provisional Patent Application Ser. No. 60/656,084, entitledOptical Tracking System for Refueling, filed on Feb. 25, 2005, thecontents of which are incorporated herein by reference in its entirety,discloses, among other things, embodiments of the present inventionconfigured for wind-tunnel scaled testing of at least some of themethods, devices, and systems as described herein. It is noted that thepresent invention thus includes the devices, systems and methodsdisclosed therein, scaled or unscaled. The present invention thusfurther includes the devices, systems and methods disclosed thereinscaled for implementation with the teachings herein.

According to some embodiments of the scaled test model, the optical linkis be visible and eye safe; the distance to the target may be about 10feet, the active area of the scan beam (scanning area) may be about 12.8inches by about 12.8 inches at the receiver; the grid resolution at thetarget may be about 0.025″; the beam spot size at the target may beabout 0.015″ diameter or less; the frame rate may be about 100 Hz; thereceiver active area may be about 0.250″ diameter or more; and thereceiver may have a field of view of 30° (i.e. a conic included angle of30°). Still further, according to some embodiments of the scaled testmodel, there may be 512×512 scan lines in a frame; there may be 18 bitsminimum of encoding information on the beam for each position on thetarget grid such that (assuming 18 bits) a 26.2144 MHz data rate will beachieved, i.e., 512×512×100=26.2144 MHz data rate; encoding on the beammay be of a form that permits quick recognition that only a partial dataframe has been received; sync and/or framing bits may be permitted,while recognizing that the data rate increases proportionally with theadditional bits; and a single complete block of position data may take0.78 μs. Such features may be scaled for implementation in a system asdescribed herein for aerial refueling. By way of example, in someembodiments, it is expected that a frame (e.g., an complete horizontaland vertical scan) may be completed with a speed such that 20frames/second may be accomplished. That is, one frame may beaccomplished in 50 milliseconds. By way of example, a horizontal scanmight take 20 milliseconds, and a vertical scan might take 20milliseconds. If there were 500 rows/columns per scan, at 20 bits perrow/column, 10,000 bits of information would be conveyed in 20milliseconds.

As detailed herein, aircraft (including drogues, etc.) are subject toturbulence. In a scenario where the aircraft 1000 is subjected toturbulence, the radiation emitter 200 will likewise be subject toturbulence. In this regard, an embodiment of the present inventionaddresses this by providing a motion compensation system (see FIG. 57for an example of a high-level control algorithm of the compensationsystem) such that, for example, grid displacement at 100 feet (slantrange) is about +/−0.1 feet, and at 1800 feet slant range, the griddisplacement is about +/−1.5 feet, in light turbulence.

The output of the receiver function may be an RS-232 data streamcontaining 3 bytes of data and running at 115.2 Kilo Baud. This data maybe only the 18 bit position information without any sync or header bits.This message may be the code for the frame that is nearest the center ofthe receiver. This may be determined by analyzing all complete frameswithin the field of view of the receiver. This message stream may repeatat 100 Hz. Synchronization of the 3 byte frame may be either relative tothe start of a complete scan frame or relative to the receiverprocessing element.

The transmitter may be self contained and may require only power appliedto function. All beam forming, scanning, and modulation elements may besupplied. The transmitter may optionally be in two parts: an opticalhead; and an electronics assembly. Separation of up to 8 inches may bepresent between the optical head and the electronics if the transmitteris a two part unit.

The mounting on the receiver may have dynamic motion up to a frequencyof 10 Hz; this motion may include both translation and rotation.Assuming an edge to edge motion over the 12.8 inch range at 10 Hz, thereceiver will move 10 inches per 0.1 s. (i.e., at a rate of 100 inchesper 1.0 s=0.0001 inches per 1.0 μs).

Although ambient light directed into the receiver may not be eliminated,it can be reduced or be made to be indirect. Moreover, although thereceiver may be bandwidth limited by the use of optical filters, theoperating wavelength may be in the visible band and, therefore, ambientlight may still be present.

An exemplary implementation of an embodiment of the invention suitablefor wind tunnel testing is as follows, and may be scaled accordingly foractual implementation.

A two-axis design may be utilized. Multiple optical paths, multiple scanconfigurations for a given optical path may be used. UV lasers or redlasers may be used. Single or dual galvanometer designs may be used. Aninternal line generator or an external line generator may be used. Infact, an “internal-external line generator” may be used, because withoutan internal line generator, the laser beam may be wide enough to appearon both the X and Y turning mirrors simultaneously, and thus appeared inthe X and Y scan fields simultaneously. An internal line generator isthus useful, but the device may also have external line generatingoptics. Indeed, in some embodiments, a single galvo or dual galvo,either having internal LG optics, external LG optics or internal andexternal LG optics, may be utilized. A single galvo with internal linegenerator may be used, having three simple mirrors. Two sizes may beused: ½″×½″ and 1″×1″. Small line generation optics are used, with asimple optics mounting. FIGS. 26 to 31 schematically represent variousgalvo designs, while FIGS. 32 to 33 b schematically represent beamemission in elapsed time. It should be noted that the axisrepresentations in these figures may not correspond exactly to those inthe prior figures. In an exemplary embodiment, the radiation emitterincludes a single line optical beam emitter, a prism, and a rotatablemirror assembly, wherein the radiation emitter is adapted to rotate therotatable mirror assembly so that a single line optical beam emitted bythe single line optical beam emitter is deflected by the mirror toproject the emitted single line optical beam in a first orientation. Theradiation emitter is further adapted to rotate the rotatable mirrorassembly so that the single line optical beam emitted by the single lineoptical beam emitter passes through the prism to project the emittedsingle line optical beam in a second orientation different from thefirst orientation. In this manner, a single optical beam projector(e.g., laser) may be used instead of two projectors (laser generators).Of course, other embodiments of the present invention may utilizemultiple generators that are synchronized to obtain lines at variousorientations.

Regarding line quality and characteristics, to obtain a beam width of0.25″ at 75 feet, using a UV laser diode with an emitting region ofapproximately one micron in width, a diffraction-limited cylindricallens of at least 3 mm diameter is used, located at least 3 mm from theemitting region. Accordingly, a line width of 2 mm at a range of 8 feet,using a 635 nm laser, and a line width of 10 mm at 75 feet, with thesame laser module may be obtained.

Since scanning may be done by a single axis scanner, rather than atip-tilting plate, scans in the X and Y directions may have differentvirtual centers. The apparent sources of the X and Y scans are separatedby approximately 9 mm in the X-direction, 13 mm in the Y-direction, and13.5 mm in the Z direction (again, these axis may not correspond tothose in the figures previously referred to herein). This has twoeffects on the scan registration at the sensor, both of which are minorat more than several feet working distance. The first effect is due tothe apparent lateral separation of the sources. This parallax errorresults in the misregistration of the X- and Y-scans with changingranges. The effect is about the same as what one would see if one held aflashlight in each extended hand, and aimed them at a single object.Objects both closer and farther away would register in different partsof the two beams. The effect is very small, though, since the virtualseparation of the sources in the actual device is only about 16 mm. Whenthe object is 8 feet away, the beam centers diverge at arctan(16/2400),or 0.38 degrees. This would result in a mis-registration of 1 mm forevery 6 inches change in range. At a range of 75 feet, it would resultin a mis-registration of 1 mm for every 56 inches change in range.Moreover, computers may be used to compensate for this. The onlypractical effect of this mis-registration is to reduce the coincidentarea over which both beams scan, as the range changes. Because the beamsgrow with range, the parallax error shrinks as a percentage of the areascanned. When the beams are aligned at 75 feet, this parallax error willcause the beams to overlap by only 90% when the range shrinks to 10 feetor so, 100% at 75 feet, and about 95% at one mile. For testing thesystem will be aligned at a range of 8 feet.

The second effect is due to the apparent longitudinal separation of theX and Y beam sources. This effect causes the Y beam to scan an areawhich is 1.3 mm larger than the X beam at any given range. This effectis negligible at all ranges where the beams are coincident.

The mirrors in the scanner are oriented to minimize errors of the scan.These errors take the form of coincidence errors, perpendicularityerrors and keystone errors. Keystone errors cause the scan to travelfarther along one edge than the other (the beam is actually sweeping outpart of a large circle in the image plane), resulting in a keystoneshaped scanned area. Perpendicularity errors cause the X and Y scans totravel at an angle other than 90 degrees to each other. Coincidenceerrors cause the centers of the X and Y scans to be non-coincident inthe image plane. The result of these errors is to reduce the area ofcoincidence over which the X and Y scans travel and, in the case ofperpendicularity errors, add crosstalk between the two axis. The mirrorsare arranged so that all of these errors are normally either zerothroughout the scan or at a minimum (zero) at the center of the scan.

Manufacturing errors in the mirror supports can move the orientations ofthe mirrors away from their designed positions, and thus cause theabove-mentioned errors to become non-zero. Typical manufacturing errorsare on the order of 0.003″. Assuming that each of the mirrors has a tilterror of this magnitude across its surface, the resulting scanned areaat a range of 75 feet would be significantly reduced.

Manufacturing errors can be corrected by building into the device an Xtilt adjustment on the X scan mirror and a Y tilt adjustment on the Yscan mirror. When those two adjustments are used to correct themanufacturing errors, the resulting scan can be restored to nearly itsoriginal condition. Even if some error, such as perpendicularity error,remains, as long as it is small, it may be effectively ignored.

The following material might be used to implement this embodiment: Afabricated XY scan mirror support block, a fabricated X scan mirrorsupport block a fabricated Base, a fabricated Y scan mirror supportblock, a fabricated Laser support block, a fabricated Scanner supportblock a fabricated Laser aperture, a Thorlabs 2nd Y-scanmirror—ME1S-G01, a Thorlabs 1st Y-scan mirror—ME1S-G01, a Thorlabs Xscan mirror—ME05S-G01, a Nuffield Technology, Inc. Scanner Mirror—10 mmX mirror, assembly, a Nuffield Technology, Inc. Scanner—Part No. HS-15C,a World Star Tech Laser Module—Part No. UTL5-10G-635.

FIGS. 34-39 present an example of a design for a scanner head, which isapproximately 4×4×4 inches in dimension, although in other embodiments,the dimensions may be larger.

In some embodiments, the scan area is 2′×2′ at 12′ distance. Operationis at 25 Hz. FIGS. 34-39 schematically represent an emitter according toan embodiment of the present invention.

Again, the above may be scaled for actual implementation.

It is noted that while the above has been described in terms ofapplication for determining a position of a refueling drogue relative toa reference point, and thus controlling the position of the refuelingdrogue relative to a refueling point, other embodiments of the presentinvention might be utilized to determine the location of other types oftargets and/or control the location of those targets. Such targets mayinclude, for example, aircraft, landcraft, boats, autonomous drones,satellites, a refueling boom extended from the refueling aircraft, etc.Indeed, some embodiments of the present invention may be implemented byplacing a radiation emitter up on a tower, and scanning an area belowthe tower, such as a runway, a parking lot, a construction site, etc,and using the invention to control/position autonomous drones,autonomous vehicles (alleviating the need for a parking attendant),construction equipment such as bulldozers, etc.

In this regard, in an embodiment where the targets are aircraft (e.g.,autonomous drones, a scan head may be placed on the aircraft 1000 sothat the scan head will generate a modulated laser line as detailedherein. The mirror equipped galvanometer rotates a rotating mirror offof which the laser from the laser diode is reflected onto various fixedmirrors to generate the scan sweep. As may be seen, the scanner headincludes three fixed mirrors. These fixed mirrors are used to form thegrid detailed above. In this regard, referring now to FIGS. 44-46, in anexemplary embodiment, as the galvanometer mirror rotates clockwise, thelaser beam from the laser diode is reflected from the rotating mirroronto a first mirror from which the beam is also reflected (see FIG. 44).Due to the rotation of the mirror, the reflected beam from the firstmirror moves from right to left (hence the scan in the Y axis isproduced). (Note that in this exemplary embodiment, the laser diodepulses at a rapid rate to form the grids of the Y axis scan.) As therotating mirror continues to rotate clockwise, the laser line falls onthe second mirror (see FIG. 45). The second mirror is oriented 45degrees from the rotating mirror at this point, which causes the laserbeam to project upward (relative to plane on which FIG. 45 ispresented). The laser beam reflects from this second mirror onto a thirdmirror (see FIG. 46) which is tilted at a 45 degree angle in the X axis.The result of the three reflections is that the line formed by the laserbeam is projected at a 90 degree angle with respect to the line thatforms the scan in the Y axis.

The galvanometer of the exemplary embodiment depicted in FIGS. 43-46 isa linear current controlled torque motor with active positioningfeedback that runs in a closed loop position control regime. In anexemplary embodiment, for a given current input, the galvanometer willrotate to a specific angle, and for a given current rate, thegalvanometer will rotate at a specific rate. That is, in someembodiments, rotation of the galvanometer may be controlled bycontrolling the current and/or voltage to the galvanometer.

In some embodiments, the galvanometer is driven with a sawtooth waveformsuch that the galvanometer is swept through an active range in a linearmanner, and then it is returned, or “flies back,” to the initialstarting point (and thus the rotating mirror is so swept). FIG. 47presents an exemplary graph showing galvanometer movement according toan embodiment of the present invention.

The radiation emitter 200 according to an exemplary embodiment of thepresent invention is mounted inside the aircraft 1000 (in someembodiments, it is a fully self contained unit requiring only power fromthe aircraft), and sometimes is mounted inside the pressure vessel ofthe aircraft, although in other embodiments, the emitter 200 may bemounted exteriorly to the aircraft and/or outside the pressure vessel.An exemplary embodiment of the emitter 200 transmits the scanning beamsthrough a 2 inch diameter quartz aperture.

When used to scan other aircraft (e.g., a receiver aircraft, which maybe a drone), it is expected that optical tracking may be executed at arange of at least about 1000 feet below and 1500 feet behind theaircraft 1000. In such an embodiment, a scan head that has a 30 degreefield of view may be utilized. That is, the scan head outputs beams thatscan through 30 degrees in each scan pass, although more narrow orbroader fields of view (e.g., 20 degrees, 45 degrees, etc.) may beutilized depending on the desired performance characteristics of theoptical tracking system. FIG. 50 presents exemplary fields of view ofthe scan head utilized in an exemplary embodiment of the opticaltracking system according to the present invention (all dimensions arein feet unless otherwise indicated, and the schematic presented in FIG.50 is to scale). In some embodiments, the optical tracking systemoutputs a UV laser beam that is safe with respect to a pilot of theother aircraft (e.g., safe to the pilots eyes, etc.). In this regard,FIG. 51 presents a performance characteristic of an embodiment of theoptical tracking system according to a present invention, although it isnoted that some embodiments need not adhere to this performancecharacteristic (e.g., in the case of tracking an autonomous drone, inthe case of tracking a refueling drogue, etc.). Some embodiments operateat a maximum permissible exposure of 405 nM/185 mW. In some embodiments,the design of the scan head outputs radiation at an eye safe level perANSI maximum permissible exposure levels. Some embodiments of thepresent invention are configured to operate in direct sunlight and inthe presence of visible moisture. In this regard, FIGS. 52-54 presentperformance characteristics of some exemplary embodiments of the presentinvention. (Note that FIG. 54 presents visibility and signaltransmission characteristics for various atmospheric conditions assuminga 45 degree field of view and a S/N Ratio>100.)

Some embodiments are NVG (night vision goggle) compatible, and have alow probability of detection/interception (e.g., in some embodiments,the scan beam is attenuated outside of a 3000 feet radius from theradiation emitter 200). The optical tracking system may provide areference system independent of a global positioning system, intertialnavigation system, etc.

Some embodiments of the present invention permit ease of calibration andinclude built in test features. In this regard, such features arerelated to the desire to obtain accurate beam modulation timing so thatclock pulses are adequately synchronized in accordance with a saw-toothwaveform. (In an exemplary embodiment, the pulsation of the laser diodecorresponds to a clock signal, and thus the pulsation may be considereda clock itself.) That is, the pulsation of the beam may be representedby a series of uniform square waves (see FIG. 59, for example). Alongthese lines, beam shift is believed to be the dominant error source insome embodiments of the present invention (due to, for example,temperature changes, galvanometer aging, mechanical damage/distortion,etc). Some embodiments are configured to compensate for beam shift byusing, for example, by adjusting the drive electronics of the system. Insome embodiments, an internal detector diode may be positioned at themirror transition point in the emitter 200 to detect damage and/orsignificant drift of component(s) of the system. In some embodiments,the output waveform is monitored for compliance to a uniform squarewave, uniform signal cycle gap, and/or equal number of edges on eachside of the cycle gap, and waveform timing is adjusted to maintain someor all of these parameters. (FIG. 59 provides a schematic representationof an exemplary scenario where the system is calibrated/synchronizedproperly and is not calibrated/synchronized properly.) In some suchembodiments, the function of maintaining some or all of these parametersprovides a built in test capability that ensures that the galvanometerand laser are operating at a sufficient accuracy level.

It is noted that some embodiments of the present invention include awarning system to indicate to a user when the optical tracking systemshould and/or should not and/or should be used with caution.

FIG. 56 presents an exemplary performance characteristic of anembodiment of the optical tracking system according to the presentinvention, where it can be seen that range resolution is about 23.1 feetat 1803 feet from the radiation emitter 200, and that this resolutionimproves greatly the closer the target is to the emitter 200. (In anexemplary embodiment, range resolution improves by approximately 2orders of magnitude as the distance between the radiation emitter 200and the target decreases, and, in some embodiments, range resolution isless than about 1 inch at 100 feet.)

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the present invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention accordingly is to be defined as set forth inthe appended claims.

1. An airborne object tracking system, comprising: an airborne objectpositioning system, the airborne object positioning system including aradiation emitter, a radiation receiver and a signal processor, whereinthe radiation emitter is adapted to be attached to a refueling aircraft,and wherein the radiation receiver is adapted to attach to the airborneobject; wherein the radiation emitter is adapted to direct radiation toa positioning area a defined distance from the radiation emitter, theradiation carrying a modulated location signal containing informationcorresponding to positions within the positioning area; wherein theradiation receiver is adapted to receive at least a portion of theemitted radiation carrying the modulated signal and output a signal tothe signal processor indicative of the modulation of the location signalof the received radiation; and wherein the signal processor is adaptedto process the outputted signal and identify a position within thepositioning area indicative of the location in the positioning area ofthe received radiation.
 2. The system of claim 1, wherein the radiationemitter is adapted to emit a focused optical beam and scan the focusedoptical beam over the positioning area.
 3. The system of claim 1,wherein the emitted radiation is a focused optical beam, wherein themodulated location signal includes a plurality of digital data blocks,the plurality of digital data blocks containing information respectivelycorresponding to a plurality of discrete positions within thepositioning area that respectively correspond to a current location ofthe focused beam within the positioning area.
 4. The system of claim 3,wherein the radiation emitter is adapted to emit a focused optical beamand scan the focused optical beam over the positioning area.
 5. Thesystem of claim 2, wherein the radiation emitter is adapted to emit afocused optical beam and scan the focused optical beam over thepositioning area in an X-Y raster.
 6. The system of claim 2, wherein theradiation emitter is adapted to emit a focused optical elongated beamand scan the focused optical elongated beam over the positioning area ina dual-pass manner.
 7. The system of claim 2, wherein the radiationemitter is adapted to emit a focused optical beam and scan the focusedoptical beam over the positioning area in a spiral pattern, the spiralpattern having a focus at the approximate center of the positioningarea.
 8. The system of claim 3, wherein the radiation receiver isadapted to receive at least a portion of the focused beam when at leastthat portion of the focused beam is directed at the radiation receiver,and wherein the signal outputted by the receiver is indicative of theinformation contained in at least one digital data block carried by thereceived radiation.
 9. The system of claim 3, wherein the radiationreceiver is adapted to receive at least a portion of the focused beamwhen at least that portion of focused beam is directed at the radiationreceiver and determine whether a full digital data block carried by thefocused beam has been received, and only if a full digital data blockhas been received, output the signal to the signal processor, whereinthe outputted signal is indicative of the information contained in thefull digital data block received.
 10. The system of claim 1, wherein theradiation emitted by the radiation emitter is a focused beam and theradiation emitter is adapted to scan the focused beam over thepositioning area; wherein the airborne object positioning system isadapted to virtually divide at least a portion of the positioning areainto a virtual grid, the virtual grid including a plurality ofdistributed distinct sectors, the distributed distinct sectors spatiallycorresponding to sub-areas within the positioning area, the sub-areasbeing disbursed within the positioning area in a geometrically definedmanner; wherein the airborne object positioning system is adapted tochange the modulated location signal carried on the focused beam as thefocused beam is scanned over the positioning area, wherein change in themodulated location signal corresponds in a defined manner to thesub-areas such that a modulated location signal indicative of a beambeing directed at a first sub-area is distinct from a modulated locationsignal indicative of a beam being directed at a second sub-area; andwherein the signal processor is adapted to analyze one or more outputtedsignals from the receiver indicative of the modulation of the locationsignal and identify a distinct sector corresponding to the receivedmodulated location signal carried on the focused beam.
 11. The system ofclaim 10, wherein the signal processor identifies a sub-area at whichthe beam is directed based on the identification of the distinct sectorcorresponding to the received modulated location signal carried on theemitted radiation.
 12. The system of claim 10, wherein the signalprocessor is adapted to analyze a first outputted signal and a secondoutputted signal outputted after the first outputted signal to determinea location in the virtual grid at which the distinct sectors coincide;the first and second outputted signals being respectively indicative ofthe modulation of the location signal of the beam received by thereceiver.
 13. The system of claim 12, wherein the signal processoridentifies a sub-area at which the beam is directed based on thedetermination of the location in the virtual grid at which the distinctsectors coincide.
 14. The system of claim 12, wherein the radiationemitted by the radiation emitter is a focused optical elongated beam andthe radiation emitter is adapted to scan the focused optical elongatedbeam over the positioning area in a dual-pass manner, wherein the firstoutputted signal is generated by the reception of at least a portion ofthe focused optical elongated beam in a first pass of the beam over thepositioning area, and wherein the second outputted signal is generatedby the reception of at least a portion of the focused optical elongatedbeam in a second pass of the beam over the positioning area.
 15. Thesystem of claim 14, wherein the focused optical elongated beam of thefirst pass is normal to the focused optical elongated beam of the secondpass.
 16. The system of claim 14, wherein the airborne objectpositioning system is adapted to identify the location of the receiverwithin the positioning area based on the coincidence of the firstoptical elongated beam and the second optical elongated beam.
 17. Thesystem of claim 1, wherein the system is part of a system assembly thatincludes an aerial refueling system that includes an aerial refuelingdevice that in turn includes an active control system adapted toregulate a position of the aerial refueling device with respect to arefueling aircraft when the aerial refueling device is extended from therefueling aircraft.
 18. The system of claim 11, wherein the radiationreceiver is mounted on the airborne object, wherein the airborne objectincludes an active control system adapted to regulate the position ofthe radiation receiver within the positioning area when the airborneobject is proximate a refueling aircraft on which the radiation emitteris mounted.
 19. The system of claim 18, wherein the active controlsystem is adapted to regulate the vertical and horizontal position ofthe airborne object to maintain a substantially fixed orientation of thereceiver within the positioning area.
 20. The system of claim 17,wherein the active control system is adapted to regulate a position ofthe radiation receiver so that the position of the radiation receiver issubstantially constant within the positioning area.
 21. An airborneobject tracking system, comprising: an airborne object positioningsystem, the airborne object positioning system including a radiationemitter adapted to be attached to a refueling aircraft, and a radiationreceiver adapted to be attached to the airborne object, and a signalprocessor; wherein the radiation emitter is adapted to direct a beam ofemitted radiation to an area away from the radiation emitter, theradiation including discernable properties that vary in a correspondingmanner with varying orientation of the beam of radiation with respect tothe radiation emitter; wherein the radiation receiver is adapted toreceive at least a portion of the emitted radiation and output a signalto the signal processor indicative of one or more of the discernableproperties of the received radiation; and wherein the processor isadapted to process the outputted signal and identify a first virtualorientation indicative of an orientation of the receiver relative to theradiation emitter when at least a portion of the radiation was receivedby the receiver.
 22. The system of claim 21, wherein the radiationemitter is adapted to emit a focused optical beam modulated with digitaldata blocks, the modulated digital data blocks respectively indicativeof discrete orientations respectively corresponding to orientations ofthe beam relative to the radiation emitter.
 23. The system of claim 22,wherein at least some of the varied discernable properties arerespectively indicative of discrete orientations respectivelycorresponding to orientations of the beam relative to the radiationemitter in a first reference frame, and wherein at least some of thevaried discernable properties are respectively indicative of discreteorientations respectively corresponding to orientations of the beamrelative to the radiation emitter in a second reference frame.
 24. Thesystem of claim 23, wherein the signal processor is adapted to analyze afirst outputted signal from the receiver, the first outputted signalbeing indicative of a first discernable property of the receivedradiation indicative of a first discrete orientation corresponding to afirst orientation of the beam relative to the radiation emitter in thefirst reference frame at the time that the radiation was received, andwherein the signal processor is adapted to analyze a second outputtedsignal from the receiver, the second outputted signal being indicativeof a second discernable property of the received radiation indicative ofa second discrete orientation corresponding to a second orientation ofthe beam relative to the radiation emitter in the second reference frameat the time that the radiation was received; and wherein the signalprocessor is adapted to identify a virtual location of the receiverrelative to the radiation emitter based on the analysis of the first andsecond outputted signals.
 25. The system of claim 22, wherein theradiation receiver is adapted to receive the focused beam carrying thedigital data blocks when the focused beam is directed at the radiationreceiver and output the signal to the signal processor, wherein theoutputted signal is indicative of the information contained in a digitaldata block carried on the received beam, and wherein the processor isadapted to analyze the outputted signal from the receiver indicative ofthe information contained in the received digital data block andidentify the orientation of the beam relative to the radiation emitterbased on the information contained in the received digital data block toidentify the first virtual orientation.
 26. The system of claim 21,wherein the radiation emitted by the radiation emitter is a focused beamand the radiation emitter is adapted to scan the focused beam over thearea; wherein the airborne object positioning system is adapted tovirtually divide at least a portion of the various possible orientationsof the beam relative to the radiation emitter into a beam zone, the beamzone including a plurality of distributed distinct vectors, thedistributed vectors spatially corresponding to actual orientations ofthe beam with respect to the radiation emitter, the actual orientationsbeing disbursed within the beam zone in a geometrically defined manner;wherein the radiation emitter is adapted to change the modulated signalcarried on the focused beam as the focused beam is scanned over the areato obtain different modulated signals, the different modulated signalscorresponding in a defined manner to the actual orientations such that amodulated signal indicative of a beam being directed along a firstorientation is distinct from a modulated signal indicative of a beambeing directed along a second orientation; and wherein the signalprocessor is adapted to analyze the outputted signal from the receiverindicative of the modulation of the signal and identify the distinctvector corresponding to the received modulated signal carried on theemitted radiation.
 27. The system of claim 26, wherein the signalprocessor is adapted to identify the orientation of the receiverrelative to the radiation emitter based on the identified distinctvector.
 28. The system of claim 26, wherein the signal processordetermines at least one of (i) the distinct vector along which the beamis directed based on the identification of the distinct vectorcorresponding to the received modulated signal carried on the emittedradiation and (ii) the orientation along which the beam is directedbased on the identification of the distinct vector corresponding to thereceived modulated signal carried on the emitted radiation.
 29. Thesystem of claim 21, wherein the airborne object includes an activecontrol system adapted to regulate the position of the airborne objectwith respect to a refueling aircraft on which the radiation emitter ismounted when the airborne object is proximate the refueling aircraft.30. The system of claim 29, wherein the radiation receiver is mounted onthe airborne object, wherein the aerial refueling system includes anactive control system adapted to regulate the position of the radiationreceiver when the airborne object is proximate a refueling aircraft onwhich the radiation emitter is mounted.
 31. The system of claim 29,wherein the active control system is adapted to regulate the verticaland horizontal position of the airborne object to maintain asubstantially fixed orientation of the receiver with respect to theradiation emitter.
 32. A method of determining a position of an airborneobject, comprising: positioning an airborne object proximate a refuelingaircraft; scanning a focused optical elongated beam from a radiationemitter onboard the refueling aircraft over a positioning area a defineddistance from the radiation emitter; modulating a signal carried on thebeam as the beam is scanned over the positioning area in a mannercorresponding to positions of the beam within the positioning area;receiving the optical beam carrying the modulated signal with a receiveron the airborne object; and analyzing the modulation of the signalcarried on the received optical beam to determine a position within thepositioning area of the receiver at the time the radiation was received.33. The method of claim 32, further comprising scanning the focusedoptical elongated beam over the positioning area in a two-pass mannerand receiving the focused elongated beam scanned in a two-pass manner.34. The method of claim 33, further comprising receiving the opticalbeam scanned in a first pass of the two-pass scan and receiving theoptical beam scanned in a second pass of the two-pass scan and comparingthe beams received in the first pass and the second pass and determiningthe position of the receiver within the positioning area based on acorrespondence of position of the beams within the positioning area ofthe beams.
 35. The method of claim 33, further comprising receiving theoptical beam scanned in a first pass of the two-pass scan and receivingthe optical beam scanned in a second pass of the two-pass scan andcomparing the beams received in the first pass and the second pass anddetermining the position of the receiver within the positioning areabased on a correspondence of position of the received beams within thepositioning area.
 36. The method of claim 32, further comprisingactively controlling the airborne object to maintain a substantiallyfixed position relative to the radiation emitter based on the determinedposition within the positioning area of the receiver.
 37. The system ofclaim 1, wherein the radiation emitter includes: a single line opticalbeam emitter; a prism; and a rotatable mirror assembly; wherein theradiation emitter is adapted to rotate the rotatable mirror assembly sothat a single line optical beam emitted by the single line optical beamemitter is deflected by the mirror to project the emitted single lineoptical beam in a first orientation; and wherein the radiation emitteris adapted to rotate the rotatable mirror assembly so that the singleline optical beam emitted by the single line optical beam emitter passesthrough the prism to project the emitted single line optical beam in asecond orientation different from the first orientation.
 38. The systemof claim 1, wherein the system is part of a system assembly thatincludes an aerial refueling device adapted to transfer fuel to areceiver aircraft extendable from a refueling aircraft.
 39. The systemof claim 38, wherein the aerial refueling device comprises a refuelingdrogue assembly including a refueling drogue and a refueling hose incaptive relation with the refueling drogue, and wherein the radiationreceiver is mounted on at least one of the refueling drogue and therefueling hose.
 40. The system of claim 38, wherein the aerial refuelingdevice comprises a refueling boom assembly, and wherein the radiationreceiver is mounted on the refueling boom.
 41. The system of claim 1,wherein the system is adapted to extract information from the radiationemitted from the radiation emitter which is received by the radiationreceiver indicative of a straight-line distance between the radiationemitter and the radiation receiver.
 42. The system of claim 41, whereinthe system is adapted to extract information from the radiation emittedfrom the radiation emitter which is received by the radiation receiverindicative of a straight-line distance between the radiation emitter andthe radiation receiver, the information being based on the amount ofradiation received by the radiation receiver during a predeterminedperiod of time, the system including an algorithm having the parameterssuch that the more radiation from the radiation emitter that is receivedby the radiation receiver during the predetermined period of time, thesmaller the straight-line distance between the radiation emitter and theradiation receiver.
 43. The system of claim 41, wherein the radiationemitter modulates an intensity of the beam according to a periodiccycle, wherein the system is adapted to extract information from theradiation emitted from the radiation emitter which is received by theradiation receiver indicative of a straight-line distance between theradiation emitter and the radiation receiver, the information beingbased on the number of modulations detected by the radiation receiverduring a predetermined period of time, the system including an algorithmhaving the parameters such that the greater the collective intensity ofradiation from the radiation emitter that is received by the radiationreceiver during the predetermined period of time, the smaller thestraight-line distance between the radiation emitter and the radiationreceiver.
 44. The system of claim 41, wherein the radiation emittercycles emission of the beam according to a periodic cycle to direct aplurality of lines towards the radiation receiver, wherein the system isadapted to extract information from the radiation emitted from theradiation emitter which is received by the radiation receiver indicativeof a straight-line distance between the radiation emitter and theradiation receiver, the information being based on the number ofemission cycles detected by the radiation receiver during apredetermined period of time, the system including an algorithm havingparameters such that the higher number of emission cycles from theradiation emitter that are received by the radiation receiver during thepredetermined period of time, the smaller the straight-line distancebetween the radiation emitter and the radiation receiver.
 45. The systemof claim 21, wherein the system is part of a system assembly thatincludes an aerial refueling device adapted to transfer fuel to areceiver aircraft extendable from a refueling aircraft.
 46. The systemof claim 45, wherein the aerial refueling device comprises a refuelingdrogue assembly including a refueling drogue and a refueling hose incaptive relation with the refueling drogue, and wherein the radiationreceiver is mounted on at least one of the refueling drogue and therefueling hose.
 47. The system of claim 45, wherein the aerial refuelingdevice comprises a refueling boom assembly, and wherein the radiationreceiver is mounted on the refueling boom.
 48. The system of claim 21,wherein the system is adapted to extract information from the radiationemitted from the radiation emitter which is received by the radiationreceiver indicative of a straight-line distance between the radiationemitter and the radiation receiver.
 49. The system of claim 48, whereinthe system is adapted to extract information from the radiation emittedfrom the radiation emitter which is received by the radiation receiverindicative of a straight-line distance between the radiation emitter andthe radiation receiver, the information being based on the amount ofradiation from the radiation emitter received by the radiation receiverduring a predetermined period of time, the system including an algorithmhaving the parameters such that the more radiation from the radiationemitter that is received by the radiation receiver during thepredetermined period of time, the smaller the straight-line distancebetween the radiation emitter and the radiation receiver.
 50. The systemof claim 48, wherein the radiation emitter modulates an intensity of thebeam according to a periodic cycle, wherein the system is adapted toextract information from the radiation emitted from the radiationemitter which is received by the radiation receiver indicative of astraight-line distance between the radiation emitter and the radiationreceiver, the information being based on the number of modulations ofthe radiation from the radiation emitter detected by the radiationreceiver during a predetermined period of time, the system including analgorithm having the parameters such at least one of: the greater thecollective intensity of radiation from the radiation emitter that isreceived by the radiation receiver during the predetermined period oftime, the smaller the straight-line distance between the radiationemitter and the radiation receiver; the greater the number ofmodulations of the radiation from the radiation emitter that is receivedby the radiation receiver during the predetermined period of time, thesmaller the straight-line distance between the radiation emitter and theradiation receiver.
 51. The system of claim 48, wherein the radiationemitter cycles emission of the beam according to a periodic cycle todirect a plurality of lines towards the radiation receiver, wherein thesystem is adapted to extract information from the radiation emitted fromthe radiation emitter which is received by the radiation receiverindicative of a straight-line distance between the radiation emitter andthe radiation receiver, the information being based on the number ofemission cycles detected by the radiation receiver during apredetermined period of time, the system including an algorithm havingparameters such that the higher number of emission cycles of theradiation from the radiation emitter that are received by the radiationreceiver during the predetermined period of time, the smaller thestraight-line distance between the radiation emitter and the radiationreceiver.
 52. The method of claim 32, wherein the airborne object is areceiver aircraft.
 53. The method of claim 32, further comprising:positioning a second airborne object proximate the refueling aircraft;receiving the optical beam carrying the modulated signal with a secondreceiver on the second airborne object; and analyzing the modulation ofthe signal carried on the received optical beam to determine a positionwithin the positioning area of the second receiver at the time theradiation was received.
 54. The method of claim 53, wherein the actionsare performed within five seconds of one another.
 55. The method ofclaim 32, further comprising: positioning a second airborne objectproximate the refueling aircraft; scanning a second focused opticalelongated beam from a second radiation emitter onboard the refuelingaircraft over a second positioning area a respective defined distancefrom the radiation emitter; modulating a signal carried on the secondbeam as the second beam is scanned over the second positioning area in amanner corresponding to positions of the second beam within the secondpositioning area; receiving the second optical beam carrying the secondmodulated signal with a second receiver on the second airborne object;and analyzing the modulation of the second signal carried on thereceived second optical beam to determine a position within the secondpositioning area of the second receiver at the time the second radiationwas received.
 56. The method of claim 55, wherein the actions areperformed within 5 seconds of one another.
 57. The method of claim 55,wherein at least a portion of the second positioning area overlaps atleast a portion of the first positioning area.
 58. The method of claim32, further comprising: scanning a second focused optical elongated beamfrom a second radiation emitter onboard the refueling aircraft over asecond positioning area a defined distance from the radiation emitter;modulating a signal carried on the second beam as the second beam isscanned over the second positioning area in a manner corresponding topositions of the second beam within the second positioning area;receiving the second optical beam carrying the second modulated signalwith the receiver on the airborne object; and analyzing the modulationof the second signal carried on the received second optical beam todetermine a position within the second positioning area of the secondreceiver at the time the second radiation was received.
 59. The methodof claim 58, wherein the first and second positioning areas at least oneof partially overlap and fully overlap, the method further comprisingcomparing the determined position within the first positioning area tothe determined position within the second positioning area to evaluateaccuracy.
 60. The method of claim 58, wherein the actions are performedwithin 5 seconds of one another.
 61. A method of positioning an airborneobject relative to a refueling aircraft, comprising: executing theactions of claim 32; and varying the position of at least one of theairborne object an at least a component of the refueling aircraftadapted to mate with the airborne object based on the determinedposition of the receiver within the positioning system to decrease arange between the airborne object and the component of the refuelingaircraft adapted to mate with the airborne object until the airborneobject and the component of the refueling aircraft adapted to mate withthe airborne object mate with one another.
 62. A method of positioningan airborne object relative to a refueling aircraft, comprising:executing the actions of claim 32; and automatically varying theposition of at least one of the airborne object an at least a componentof the refueling aircraft adapted to mate with the airborne object basedon the determined position of the receiver within the positioning systemto automatically decrease a range between the airborne object and thecomponent of the refueling aircraft adapted to mate with the airborneobject until the airborne object and the component of the refuelingaircraft adapted to mate with the airborne object mate with one another.63. The method of claim 32, wherein the airborne object is an autonomousdrone.